This.

Halo 2 is the only over rated one, and thats slightly.

I have played Halo 1 &3 and both of them are average 7/10 or 8/10 games at most.

This series became big only because it lacked any serious competition on consoles.

that doesn't explain why they are still so big. I think you'll find that the reason it did so well was because the story line is pretty decent, the gameplay has been left unchanged for the most part ( meaning no matter which Halo you pick up, when you play, it feels and looks like Halo), and the multiplayer beats pretty much everything out there in terms of fun.

Dude, have you actually done research or just making crap up in order to make yourself seem superior or elite? 

The PC Halo port has garnered very positive reviews.

http://www.gamerankings.com/pc/291594-halo-combat-evolved/index.html

It's arguable that Halo does rank up with classic PC shooters like Half-Life and Doom, I would explain why but I will allow former senior editor of GameSpot Greg Kasavin A.K.A. Best Game Critic Evar!!! to do that for me.

Does this question deserve an answer?

Why not? this is a forum after all!!!

You're splitting hairs, I'd consider an 86 on gamerankings (83 on metacritic) to be pretty mediocre.  There were good parts, the score was great, the atmosphere was good, but the level design was just piss poor.  And while I thought the vehicle sections would be great, I felt the control scheme (pointing the camera rather than controlling the vehicle) really ruined it.  I'm not saying the game was terrible, it was just mediocre.

Millions disagree with you. 

Are we going by sales, now?  I guess that makes Britney Spears an excellent musician and Michael Bay a master filmmaker lol.