Spyro. Anything after Spyro 3 and 4 were completely stupid and the developers should be shot.
Also Halo. The first was good, the second was also relatively good, but Halo 3, and Halo 3: ODST were probably some of the worst games I have ever played. Halo: Reach picked the game up again, and Halo 4 should be good.
CoD too. CoD 4 was good, but since then it has just gone downhill, each infinity ward game is repetitive and treyarch just can't develop good games
I strongly disagree. Spyro: Season of Flame and Spyro: Attack of the Rhynocs were great games.