reverb is essentially many many short delays. like playing in a small room with the sound continually rebounding back and forth.
i think what makes oasis and such sound big is the 4x12s they use. maybe you could try a cab simulator of some sort?
OT, but does anyone know of any digital(yes digital) delays with a fair amount of delay time, trails when turned off and can be modded with hi-cut to sound more analog?