After reading the Wiki, I found many things that I missed.

So Rapture is just a variable of Columbia? Andrew Ryan is just another Comstock? It all ceases to exist? The events in the original Bioshock thus never happen? It's all a variable that ends with the drowning of DeWitt?

I suppose we will never have a BioShock ever again. It's pretty depressing, but after this ending, the most noble outcome.

I like the game, i like the story told throughout, i followed it along, i grasped the travelling through a multiverse.
(imho the game isn't time travel, but travel through planes of existence where time isn't multiverse standard just each universe is at a different time)

i just really dislike the ending, i hate the idea that after so much the fate of Booker De Witt cannot be changed... in a multiverse setting... where all possibilities and probabilities, and have, and will go on to occur...

something feels very wrong about the ending, I'm not sure what it is, but i have a strong gut reaction to dislike it. i think the finale felt a bit lame, the final chase for comstock (booker de witt reborn) was a bit of a let down when you get there, yes i understand its a plot point to help underline how horrific the ending is for booker.

the actual visual representation of infinite possibilities through the lighthouses was cool, but i disliked the lack of paths you could take though, i wanted to keep wandering and wandering through the maze of lighthouses to "choose" my own fate.

i feel the skill element was taken away, any element to imapct the story was taken away, yet you are forced to follow a path to rebirth then death. i understand this was to underline the fate of booker de witt, but i argue due to the infinite multiverse, there is one booker de witt going round smothering all booker de witts, by process of elimination changing the fates across the multiverse. so its sort of a self defeating thing this ending, atleast one booker would have been able to kill the infant bookers.

literally finished the game about 10 mins befor long post, hope you enjoy the read.

I personally don't believe that there's any connection between the characters of the first Bioshock and Infinite. 

Like Elizabeth said there are constants and variables, but I don't think the variables are THAT different, the cities aren't even similar. Elizabeth said: "The same, yet different" so it doesn't make sense for them to be the same. Also Andrew Ryans is way too young to be the same as Booker, in 1912 Comtock was already an old man, and Bioshock 1 took place in the 50's, so it doesn't make sense unless Andrew Ryans also had a way to travel to other universes lol.

I don't know, I suppose it's one of those things were your imagination goes wild and you just want your own interpretation.

I just got the game and finished it last night too. Played it for about 12 straight hours lol. Anyway, I understood some stuff but went online to check out what other people thought about it. I found this

http://venturebeat.com/2013/03/28/understanding-bioshock-infinites-ending-ending-explanation/

Take a read, everything makes sense to me now, and for the most part across other forums what the author says in the link I provided is what most people also believe.

The multi-dimensions concept in this game is quite simple, and yet very undercoocked. And they messed it up specially in the ending.

Just because another you in other parallel universe did somethings, it does NOT mean at all that if you die, the other will cease to exist and all what he has done will be undone. It is just ridiculous and poorly done. They try to complicate things just for the sake of doing so, and it does not ads to the experience because it is badly done.

So, Booker at the end realizes that he is in one of infinite paths, that offers similar events and consequences. And he notices that "he" in other parallel reality is Comstock, so he "allows" Elizabeth to kill him during the baptism which would mark the "birth" of Zachary Comstock, and thus eliminating all he has done, including Columbia; his racist, xenophobic, and patriotic crusade; and the harm done to Elizabeth. The problem here is that, the Booker that is the one who is being killed is not the Booker from the reality in which he is Zachary Comstock, so killing him wont change anything about Comstock destiny. It will just cause Elizabeth to to cease to exist, because his father is dead before the moment of her conception.

And even if that point was THE point in which multiple divergences will occur. It still has not much sense, because it would mean that previously to that event there was only 1 space-temporal line, and just because booker decides to do or not to do certain thing it will create "infinite doors", infinite possibilities? For real? What makes him so special that whole reality is affected to what the hell he does?

If you want to take it further, the one that should be killed is not the 40 years old Booker we are playing as, it needed to be the actual 21 or so years old Booker in that certain event.

The whole ending was made with the purpose of "mind-raping", but it is just poorly done in the end. And also there are other mistakes about the parallel universe concept throughout the game, but are not topic on this thread though.

DeWitt is the last name of a physicist who had studies related to the interpretations of multiple worlds.

Good Job Levine.

Before the baptism there were millions of other Bookers living in different universes, but in all of those there was only 1 dimension where Comstock born (the only one that interest us from the story of the game). Now after the baptism there were 2 dimensions (remember there are millions of other universes, but for now there are only 2 that interest us): 1 with Zachary Comstock and 1 with Booker Dewitt. After the baptism every single decision either of those 2 make (even if it's just flipping a coin) created 2 different universes, and from there you had millions of "doors". Now, there could be 1 universe (or multiple ones) where there is a Zachary Comstock but no Columbia, or a Comstock that's not sterile, or one where Booker didn't had a child, the possibilities are endless.

Now, lets focus on only 2 dimensions, in one of them Comstock was sterile, so he had to take the child of Booker. Then the Lutece give Booker a chance to recover his daughter and thus the events of the game happened.

That brings me to your question, Booker is not special, his decisions created thousands of other dimensions, but so as the decisions of any other characters in the game. If the kid that gives you the mail at the beginning of the game flips a coin then that will make another dimension, but that one doesn't interest us, the ones that we see are the ones that are around Comstock, Elizabeth and Booker, those are the important ones.

Now the more interesting question, how did killing Booker Dewitt also killed Comstock where the one we killed is not the same as the one 20 years ago? Well I have 2 theories: 

1) By going throw the last door, you go back to the real memory of the Baptism, the person you control in that last moment is no longer the Booker Dewitt you used in the entire game, but the Booker of 20 years ago, only that you have the memories of the events of the game (this somewhat makes sense because throwout the game you start remembering things of your other self in other universes (one of the reasons you start bleeding from your nose), so when the Booker you control enters the dimension, the the real one from that time also "remembers" the events of the game (the only difference is that there's no nose bleeding, which me make kind of dubious about this theory)). You as the Booker Dewitt player no longer "exist", Booker said to Elizabeth (before entering the door) that he was ok in killing the source of Comstock, so Elizabeth simple go to the time of the baptism and fulfill Booker's wish.

2) The Booker in the game (the one you control) is actually THE original one that created Comstock, so by dying at the same spot it created the same memory that happened 20 years ago. This goes with what I mentioned in my first paragraph, there was only 1 dimension where the split happens, and from there there were millions of other universes. If one Booker Dewitt that was "created" after the events of the baptism dies like in the game, then it wouldn't matter because he was not the source, it HAD to be same Booker from the same universe that created the original Comstock. 

Don't take any of this stuff as factual, this are my personal theories of what happened in the game. And like I mentioned in my second post of this thread, making theories of what happened is what makes this ending so amazing imo. 

http://n4g.com/news/1218730/bioshock-infinite-ending-explained-what-does-it-all-mean

Very good article and there is even more in the comments section, think it summarises it nicely

What is the connection with Rapture?

A man, a city, another man, a lighthouse. Rapture and Columbia do not exist in the same universe. Booker may or may not come from the Rapture universe, but does not come from the Columbia universe. Fink appears to have got many of his ideas from the Rapture universe. This is also presumably how they got access to music that would not be written for several decades.

Elizabeth ceases to exist?

Yes. Anna, however, does not.

Is there a Columbia?

Not anymore.

What happened with those damned twins?

They're not twins, they are different versions of the same person. Robert is from Booker's universe; Rosalind is from Comstock's. Both were killed by Comstock in one universe, but their exposure to the machine allows them to travel between universes, effectively making them immortal.

And I concur with your opinion of the game, as does Naznatips, but unfortunately Machina still prefers BioShock