Doom 3:
Not a bad game in and of itself, but it was a complete departure from what Doom used to be. The music I understand, since a console Doom had an ambient score, but I vastly preferred the way they did it in Doom 1, Doom 2 and even Quake 2. And to make matters worse, I understand WHY they did it. Doom 3 was not a fast-paced game. There were no constant streams of enemies to shoot like in the previous Dooms and you weren't able to move nearly as quickly. STILL, the trailer music (also the menu music) was a grotesque teaser for that which was never to come, and I kept expecting it to start after I was done with the slow opening act of the game.
I'm going to go out on a limb here and say that perhaps Doom is not ruined by Doom 3. Maybe by the time they make Doom 4, they'll take the series back to its roots. Personally, I view Serious Sam as a closer spiritual successor to Doom than Doom 3 will ever be.
CoD: Modern Warfare 2:
Not balanced for lean, no dedicated servers and a smaller player count than the previous Modern Warfare. For me, it's ruined, and I get crucified by the fanboy community for ever bringing it up when I'm on a server.
Battlefield: Bad Company 2:
What a tease this game was. After so many years, people are expecting Battlefield 3, and right up until the last minute, even doubters like me had our fingers crossed. Even Modern Warfare 2 has prone. Bad Company 2 has neither lean nor prone. Their excuse? It would slow down the gameplay.
EXCUSE ME, but someone else lying face first in the dirt did nothing to slow me down from running up and stabbing them to death. In the foot. It was a great way to briefly avoid being spotted by snipers, tanks, helicopters (at certain angles) and everything else. The most common argument I get is that since cover can be blown up, it would be a useless feature. To that, I say no: it would be a balanced feature!
Beyond that, Battlefield is supposed to be a mechanized-oriented game. Trucks, tanks, choppers, boats, planes and (in '42) ships to go around. Even without prone, I still tolerate it a bit more than CoD6, but I'd much rather be grinding another two hours out on Karkand.
And what is it with the diminished classes? Choose medic and you get a LMG? You have to unlock medic stuff?
MEH!
World of Warcraft:
The RTS element of Warcraft was buried alive by this MMO. That's enough of a reason to say it ruined the series, good or bad.
