I'm surprised and pleased to hear you say this. I've been grimacing a bit as Spycraft tries to be more of a generic system, and less of 'just a spy game.' What I loved about it when I read it is that seemed well thought out to blend into it's genre, despite it's d20 roots. It takes more than just a glossy overview (d20 modern) to change the genre a game was intended for.
I want them to focus on being a spy game, but I believe I may be in the minority. It was only my years of experince that convinced ANY of my players to try it at all (and they now love it) but It shows me that Spycraft may need to be more than a spy game to stay alive and make money. Sigh.
I also don't really want one game for every purpose. I like variety, and I get frustrated when my group pins down to one system.
My favorite systems and some limitations of them.
1> Hero. Hero is one of the orginal 'generic systems. I played Fantasy Hero way back, since we were all so fond of Champions. I even ran a 4th ed FH game for a few years. Despite this, running FH feels a bit like running Fantasy Superheroes. A valid genre perhaps, but not really a Fantasy Game, as most people envision it. The freedom tends to make players ask for unusual races and characters more often, and makes the group a bit more bizarre. I loved my FH game, but it was not a true fantasy game.
I also ran a historical game and tried to use FH. It still didn't work really well, because it's just not what the game was designed to do. The game flourishes when you have the freedom to do the bizarre, and it's strength is the breadth of character concepts avaiable..restrict them and you weaken the game.
2> Spycraft: It seems great for a spy game. It seems to have added enough to D20 to make it useable, and flourish. The gear system makes a James Bond game feel doable for the first time ever.
However, as you steer away from spy games, the gear system looses it's pizzazz, the chase system seems less needed, and it reverts to being d20 modern again, with a couple of extra conditions and rules. I don't think I'd ever run a Fantasy Spycraft game, though having options there makes the variability of spy games nice.
3> Rolemaster. Rolemaster is to me the best fantasy game running. However, Modern rolemaster is virtually unplayable.
4> Deadlands (pre d20)..I loved this game system. The world needed some tweaking, but I loved adding 'cards' to a western game, and the initative systems, and a few other doo dads. Magic was just plane FUN to use. I'd never run Deadlands with another system, and I'd never use the deadlands system for another game. It's perfect for what it does, useless for everything else.
5> Eternity and Scion seem ludicrous, trying to build essentially superhero concepts into a system designed for dark gritty horror. I can't even get through the books, much less play the game. I played WW for years, currently play Werewolf, and have absolutely no desire to incorporate these odd shifts into the world.
In short, I try to find the best system for any one game. If a system can be used for more than one game, I don't really care, because there's probably a better one out there for that one, and even if their isn't..part of the fun is in trying. I love playing new systems, and I hate getting cut off from exploring them.
We spent years sort of 'locked in' to hero, and I finaly just quit playing it all together for awhile, so we could try other things. It seemed to need to be a complete break because it was so easy whenever I came up with a concept to try hero, even when it wasn't the ideal choice.