|Ha Ha - no ...|
I don't think there is a perfect game out there and in a way there doesn't need to be. in my experience games tend to be better when they specialize in a particular style or genre or level of complication. There's no reason to limit yourself to one game or even one system.
|Also a "no"|
- For example, I love the Hero System, especially for supers and I like it a lot for fantasy as well. I tried playing "Western hero" once and it was terrible - it just did not emphasize things I wanted from a western game. The system is great for a lot of other things though.
- I see people trying to turn old school D&D into various genres and most of them are just not my cup of tea, I played a ton of D&D/AD&D and had a lot of fun but there's no way I'd be looking to adapt it to some of the stuff I see coming out. Why not use a system built and tuned specifically for that type of game?
- The whole d20 thing has proven more versatile than I ever expected. From Pathfinder to Mutants and Masterminds (as my main current uses of it) it's amazing to me that those grew out of the same set of mechanics. Spycraft was another one that had an interesting approach and made me actually consider using these mechanics for a genre I never would have considered before. As much as I like it though, I don't always want levels and rounds and some of the mechanical heft that d20 brings.
I love the wide range of games we're seeing now, from simple PDFs to 500 page full color hardbacks on every subject and setting you can think of and so widely differing in mechanical approach you might wonder if they're even in the same hobby.
All that said if I had to narrow it down to one game it would probably be some yet-to-be-distilled combination of Hero for flexibility and Savage Worlds for play-ability. I'm not sure what it would look like but if I'm using existing games as a guide that's where I would start.