I like WFRP because I like the dark humor, the horror, and the heroic feel to it. Mechanically, it plays fast, and there are lots of advancement options without a lot of complexity in character design. It has a great style to it.
RQII is good and all, but honestly, there is a level at which many systems, particularly stripped down percentile systems, leave me thinking, "Ok, this does the job, but it's not any more dynamic than GURPS, and far less versatile." I do like the gonzo RQ style fantasy, though.