I'd be pretty annoyed at a global reset of scores.
I like having my unlocks, they add variety to the game. When I get bored playing a Medic I can switch weapon and try it out with a different gun. I've been playing for nearly a year, and I still don't have the full set (getting close, but that last hurdle's a big 'un.)
I don't care about the leaderboards, I know I'm not one of the best players out there, and there are people with a lot more time available to put into the game. The reason I like my stats is because they let me keep track of how I'm doing. I get to see which kit needs more time, whether or not I need to work on my accuracy, how much I'm improving as a jet pilot, and all that other stuff.
If there was a reset, I'd probably still play, I guess, but I'd be pretty annoyed. If you want to see how you'd do against other people, get a gang together and start new accounts. Put all those new accounts onto a new BF2s leaderboard, and see how you get on. Who cares where your stats put you globally? Does it really matter if some guy you've never met who spends thousands of hours throwing grenades on Karkand has a better K/D ratio?
Also, I kinda like Sarge's idea too. Extra points for making kill-streaks would give people incentive to try and keep themselves alive, rather than suicide-rushing somewhere just because they know that the worst that can happen is a 15 second wait.
