Indeed, Unreal didn't really appeal to me, and IIRC it was buggy as hell when it came out. I already had Quake2 in my wish list, so I bought that instead. I did get to play Unreal at a friend's house, but we both agreed that it wasn't just there for us, and of course the multiplayer sucked.
Half-Life, however, was a much better experience. I didn't get to play it 'till 2000 though, and it was still an awesome game by then. Definitely kicked Unreal's socks, both in single player and multi. Hell, it spawned Counter-Strike which spun off into its own game! The other mod I've seen evolve into a full-blown game is Team Fortress.