It's a fantastic album.But taking every song separately,i think their best songs were post-Definitely Maybe.The Masterplan for instance,is the best song they've ever written IMO.But it is so grossly underrated.
I actually find Liam's vocals irritating on a couple of Definitely Maybe songs.Cigarettes & Alcohol and Shakermaker for example.He does brilliantly on some other songs like Live Forever,Columbia and Supersonic.