Hmmm... I've played quite a few FPS in my time on the PC and Console, and I do not rank many as highly as the average Halo, and none as high on the awesome lets make a cool custom game and splitscreen/systemlink/online that sucker'o'scale.
It is a good game, it's just not your cup of mocha. Some people like Tech Demos more than good, unique, fun and polished entertainment software. Whatever floats their swimming aids I guess.