Gotta be Deus Ex - they took one of the most critically lauded games ever and managed to practically kill it with one of the most poorly judged attempts to mix a PC game with an Xbox release for the sequel.

Heck I almost never got into consoles at all I was so pissed with how the 'Box seemed responsible for ruining a sequel I was looking forward to more than any before or since.

That takes some serious effort beyond the usual killing of a franchise by milking it to death IMHO.

Command & Conquer - Loved the original, loved Red Alert & Aftermath, but downfill after that. Gave up after Tiberiun Sun.

Gran Turismo instantly pops into my mind, nothing has ever been as fast or as exciting as GT2.

Tony Hawk is a definite as well, that series died with THUG, I tried ever so hard to love THUG2 to no avail, THAW can go to hell, Project 8 I haven't even looked at and from the demo of Proving Ground, the series is completely dead to me. THPS2 & 4 FTW!

I agree that FFXII sucks, but not for the combat system, wich was very good IMO. I hated that they took what was one of the best elements of the series and turned it into one of the most useless elements in XII, I'm talking about the summons, FFXII's espers, I never used them because they simply don't work on any attack strategy, also they drain the bar that also gives you the oportunity to make the game's best attacks.

Also I hated that you couldn't really set characters apart, you had the abilities chessboard with the same elements for every character, so everyone could have the same abilities, weapons and strenghts, and something I love about JRPGs is that you can have very different characters with different abilities, something that just wasn't on FFXII.

The other element about FFXII that I hated was the story, it was almost like a copy from Star Wars, if you don't believe me then send me a message and I'll explain because I won't spoil it, but from start to ending the game's story is a copy of Star Wars. There is no character development at all, I wanted to know about everyone (how Balthier and the bunny got together for example) but there was just no explanation. Vaan (the main character) is uninteresting, he has no backstory, he is not important to the story and it's never explained why he can see the prince's ghost, wich really bothered me...

Now some people are saying that after FF7 the series is getting worse, but I have to disagree, FF8 wasn't very good, but FF9 was, and FF10 was a total masterpiece, I can't believe some people forget about that game...

 One thing I've tended to notice over the years is that people who played the SNES final fantasies tend to rate one of them (usually 6) higher than 7, where as you've mentioned, those that were introduced to FF on the Playstation tend to consider 7 the greatest. This was due to a combination of things including the game pushing technical limits at the time and being one of the more commercial jrpgs. Those that had played previous ones already had expectation of what made a great final fantasy, and fancy graphics and sound didn't make up for what they felt was lacking.

Yeah the Tony Hawk series of course, even way before Skate came out.

What?

Turok.

The first two fantastic games have been ruined by horrible sequels. A lot of people laugh at me when I say that Turok: The Dinosaur Hunter is one of my favorite FPS games because they have only played the newer crappier ones. Bad sequels unfortunately attach a stigma to what would be looked at as a phenomenal piece of art. Look at the movie Halloween. A lot of people say that it sucks because they haven't seen the original and associate it with Michael Myers getting into a fight with Busta Rhymes.

Final Fantasy because of XII. Whether I enjoy the mainseries from now on will depend on XIII.

Another would probably be Crash Bandicoot after Cortex Strikes back (no 2) and Tony Hawk after no. 3

Same as Fazz