The beatles had a much bigger opportunity in those days than bands have now. They started off playing rock & roll really, and things progressed from there, but I think it's unfair to use the Beatles as a yard stick for modern day talent.
To be fair to Oasis, they have offered a mixture of music from heavy to ballad, and have had a pretty good run in a market well known for fly by night bands.
Radiohead have done that though, which is why I think they probably stand alone amongst modern bands in that pantheon of 'greatness'. I think the White Stripes are superb for instance but wouldn't class them as great, even though I think Jack has more talent in his little finger than Liam and Noel combined. Horses for courses isn't it?