Well I would think that one would say that I like 68040 because that is the processor that is in my Amiga 4000, or maybe the 68060 because that would be a much better processor to use then a very slow 68040.
But I'm going to go back to the lonesome 68000, because that is the one that is so rooted in many of the projects that I've dealt with. Closest to the 65c816, so I remember all the SNES /Super Famicom demos that were coded for that. I remember that the MegaDrive/Genesis had a nice little 68k. The Saturn's CD processor was a 68000, and it made it a nice loader for many of the advanced 2D arcade style games at that time. Also the TI-92 Platinum calculator has a 68000 too.
I would have to say the 68000, because it was part of so much action.