Actually, Crysis has the ability changing gimmick, and stages far more open than is standard for FPSes!
Older FPSes actually had fairly open ended stages. It's only recently they've moved back away from that and it's lame as heck that they have., especially since the trend for more open ended environments started with, I don't know, Hexen?
BEEP BEEP GET IN THE JC DENTON.