Biggest disappointments I can think of:
Every Final Fantasy ever IX - I bought every Final Fantasy game I could get my hands on, everything after IX just didn't click with me. I even bought the PS2 hard drive to play Final Fantasy online. Bleh. The story seemed to have gotten a lot worst and the way they changed up combat? *shakes head* Western RPG developers have won me over since.
RE5 - SHIVA! SHIVA! SHIVA! SHIVA! SHIVA!
Perfect Dark Zero - Since Perfect Dark is on XBLA It's so easy to see how big of a let down this game was. The only good thing about it was 32 players online and lots of bots to throw in. Everything else was a let down.
Gears of War 2 MULTIPLAYER - Halo 2 might have had a meh single player, well Gears 2 had horrible online. I played the original gears 600+ hours online, and only put in maybe 30 hours into Gears 2 online. They somehow screwed up the entire online experience. Luckily they redeemed themselves with Gears 3.
Crackdown 2 - The first one was OK, but in the sequel they rehashed the entire game. The city is almost identical and the things you do are almost identical. wtf?
It's just that simple.
