My favourite version was V4.5. The games where alot more fun than most of the other games and the Characters where different than most of the other versions. Personally, I found it the most fun and interesting version but that's my opinion.
I like all of the ones listed for different reasons, but I voted for Music Star because I find that one to be the most complex and I like the whole music theme and everything. I also like the Music City website a lot. It's just the most fun version, in my opinion.