If you like Jak & Daxter you'll almost certainly like Ratchet & Clank. Very similar style games.
You could probably pick up DA:O Ultimate Edition for around $20-$25 and get the Awakening expansion and all the DLC with it. If you enjoy that style of RPG, you'll get a
lot of hours out of it.
inFamous is great fun, but it is incredibly short. Same with Uncharted 3. I enjoyed Arkham Asylum, but haven't played Arkham City yet. A lot of those games are definitely short, but you can pick 'em up for around $20 and get a decent amount of gameplay out of them. Then again, this is from me going through and

ing them, so playing through multiple times on the hardest difficulty kind of skews the amount of time I spend on them.
There are a bunch of great games, but it really does depend on what genres you actually enjoy playing. If you get that bundle with PS+ you were talking about the other day you'll get a ton of games to try out over the course of the year, which is nice. The only shitty thing is they disappear if you don't renew.