It all depends on the pilot although the SU27 can out turn the F-15 a good pilot can still out manouvre the SU27 by using the right manouvres. Same applys to the Mig29.
True thats what Slammers are for but as far as LOs concerned I've flown F-15s and beaten Mig29s and SU27/33s gunzo and then also been beaten by F-15s when flying the russian jets. ROE for LO is basically destroy the other side.