It's hard not to like a game's comic relief, and he really does have some hysterical lines. This is particularly true when coupled with his rapid fire delivery. Still, I agree with you, Mordin did end up being a much deeper character than I'd have initially thought he could be. When it came to the genophage, I actually found myself agreeing more with him ("had to be done" ) than with the Paragon dialog options ("you did wrong, period". I was especially interested in the conversation where Mordin expressed regret at his species role in the elevation of the Krogan in the first place. He claimed that if the Krogan had been allowed to develop naturally, they'd have had to let go of many of their violent tendencies in the process, and could have been good galactic citizens.

Anyway, he definitely presented a lot of moral dilemma, and I liked him a lot.