Now?
UT came out before Quake I think. If not then it came out pretty close to the same time. UT was my first online shooter that I got involved with. At the time I thought it was one of the best games out there. The UT engine is actually used in some other existing games. One or more of the Tom Clancy games uses that engine currently.
I am actually looking forward to how UT3 will turn out.