Portal 2 is a superior game in terms of quality. But I enjoyed playing Portal 1 a bit more.
Problems with Portal 2:
-Too easy
-GLaDOS suddenly becomes human (even near the start). Her voice has all these emotional inflections. In the first Portal, she sounded like a Computer. In Portal 2, she suddenly has way more personality, just seemed a bit weird.
- Puzzles were incredibly linear in their design. One look, 1 wall I can shoot a portal on...gee, I guess I have to go that way...yawn.
- Lack of challenge chambers ruins replay value. I've gotten ALL the single player achievements, no reason to play it anymore. I hope to get into co-op soon, waiting on a friend of mine to play that with, hopefully we don't burn through that too fast.
- This is just a nit-pick, but the ending song, "Want you gone" is pretty forgettable, not nearly on par with "Still Alive". My favorite part of the ending is the Turret Opera.