>Their music always seemed middle-of-the-road and nondescript to me - a bit too "Beatles Lite"

This is my issue with them as well. wonderwall is their one unique contribution (and actually quite great)--when I started actually listening to their albums in full I was shocked. People actually think they were competitive with guys like Blur? Blur was actually doing something rather unique. Oasis as just part of that dead-end 60s nostalgia wave that haunted the 90s.