My top of old
Mark Kerr, Vitor Belfort, Bas Rutten, Ken Shamrock
Top of current
Lyto Machida, Rousimar Palhares, Josh Barnett, Dan Henderson

My picks based on the fact that, these athletes have something worth watching. Whether it's pure brute strength and putting on a show, or a different technique and style from the mma herd, these guys are fun to watch.