Thinking about it i came to a stunning conclusion.
Since i never really played (as in: i never finished them) any adventure games, moneky island, day of the tentacle, sam and max etc. are out.
I don't think Portal was that funny to be honest. I had a few good laughs, but other than that it seemed far too serious. Same goes to a lesser extent for Portal 2.In addition i hate Wheatly with a passion.
Serious Sam has funny gameplay and monsters but isn't really that funny in itself.
Why people consider Borderlands funny is completely beyond me, i can't remember anything funny about that game. Maybe i just have a shitty memory (or sense of humor).
Dwarf fortress is really funny at times and while this is most definitely part of the game design the humor always feels a bit detached from the game. I really don't know how to explain it, sorry.
So in the end i might actually have to go with DA2. The Companion dialogues were in my opinion the best thing about the game.
I'm actually pretty sure that i would be able to think of a better game, but right now nothing comes to mind.