There's a lot of good ones and as a collector of original artwork I love asking myself these sorts of questions all the time. I like Gordon Morison a lot, and Dave C's stuff is really cool but its just not my era. For my money I like Youssi.
I have collected a few of the original backglass paintings that were made by hand before production. They are really a sight to behold in person so if you are ever in the area when one or more are going to be displayed, take advantage.
Seeing an original is realizing that you were previously looking at something with 1/10 the resolution and color.
