Yeah, I loved Unreal 2 as well... Some of the missions were kinda short, but I thought it deserved a lot more enthusiasm and interest than it received. Mind you, everyone was already playing UT2k3 by the time Unreal 2 came out. That may have hurt things.
(I am one of the people who would say Unreal and the Return to Na Pali expansion are "so-good-you-can't-miss-it" but I don't know if that opinion is warranted. I really like them still, and I can't imagine playing Unreal 2 or any of the UT games is the same at all if you don't have that kind of familiarity with the backstory / universe / Skaarj etc... I mean, how much is lost when you tell a Skaarj UT opponent that he fights like Nali when you don't know about the Nali?)