I was chatting to my good friend Chris by Email the other day, and I commented about other milieu's I would like to play in - and that I wanted to use DnD (or at least the D20 system in some form) as the basis for all our RPG'ing in the future.
Why I hear you ask (well I don't, but you get me) . . . .
1 - Playability. Its a system that works, not I know a lot of people don't like Experience and Level systems - but we do. They may be an abstraction, but for heroic style Role Playing they are brilliant. Plus in real life many people make a big deal over 'Experience' and such systems represent gains in experience (and training) well.
2 - Familiarity. One of the things that can stall any Campaign before it even begins, is lack of rules familiarity - this applies to both players and games masters. If you are playing a D20 based game, all the basic systems are the same. There will be few (if any) new systems and rules amendments to learn.
3 - Fun. The BEST Gaming experiences of my life have been with DnD or the D20 system - period! Both as a DM and as a Player. I know my group feels the same way.
A (short) list of non-DnD D20 Games, both official and unofficial.
Call of C'Thulhu
Star Trek/Prime Directive
And so on . . . . . .