weeellll, stealth is never "compromised," planes aren't invisible, they can just get closer to radar without being detected. Even if an F-22 is detected, it can get closer then it otherwise could, and it can break radar-seeking missiles lock easier.
Actually, last I checked, the MiG-21's power/weight is slightly better then the F-4, but not by much. Also, the MiG-21 doesn't really turn that well (look at the little fucker, it's a tiny dart,) but neither does the F-4, and they both roll quite well.
It's all down to pilot skill, since there's no obvious performance disparities I can peg, besides the F-4 being significantly faster.