I didn't know how to answer this, because while I think vanilla RTW sucks, and doesn't deserve more than a 4 or 5, I just installed RTR and suddenly the game has become a lot more fun, at least for now.

So I've compromised and given it a 6. Playing RTR has made me realize the potential this game has, which could be achieved with a bit more tweaking and polishing from CA. What I'd especially like to see are, obviously, improved campaign and battle AI, a better strategic balance (something to be done to stop the steamroller effect), a better developed diplomacy (for example, factions should gang up against any faction which takes the lead in number of provinces, until they knock it back to average size, as in games like Imperialism II) and more moddability. Come to think of it, it probably wouldn't be that hard to make diplomacy itself moddable, that could make for some pretty interesting mods...