Four games come to mind from this gen. All were below expectations for their franchise in at least one aspect. In order:
1. Final Fantasy XIII- took everything that makes Final Fantasy great and threw them out the window transforming it into purely linear game with an RPG battle system.
2. Dragon Age 2: good story and characters but horrible combat that relied on endless waves of enemies for difficulty thereby removing all strategy that was present in Origins. The re-use of assets and level design was also unforgivable.
3. GTA IV- after San Andreas, this was a major step back for the series; less vehicles, smaller sandbox and annoying phone calls from "friends".
4. Duke Nukem Forever- all that time waiting for a game that feels like it should have released in 2004 (if not earlier).