One of the great pop songs of the 1990s was Oasis' "Wonderwall." I'm not even a big Oasis fan, and their "nü Beatles/battlin' brothers" schtick got real old real fast, but for that one song at least, they met every potential they ever had. A plaintive, hopeful and sweeping piece of pop, with its great primal chorus of "Maybe/you're going to be the one that saves me" --it's one of those songs that just works for me, and every time I hear the original I'm transported back to 1995 or so and that weird post-college abyss of hopeful fear and strangeness your life is in before you settle down to the job/wife/kids life. It's a song of the moment and a song that seems new to me each time I hear it.
"Wonderwall" is also one of the more covered songs of the 1990s by alt-acts, although it's always done with a vague sense of embarrassment (if Oasis were cool in 1995, they sure aren't in 2004). Ryan Adams did a lovely, almost holy cover on his "Love is Hell Part One" CD last year and it'd be perfect if it weren't for the goofy faux-Cockney introduction he gives it. Cat Power, she of the lovely cover songs, did a lush and gorgeous spare version I recently downloaded, while Weezerapparently also did a decent cover I've found. I've seen another on Limewire by The Beastie Boys of all people which I'm intrigued to hear but wasn't able to get earlier. I also downloaded an atrocious "drum 'n' bass" remix of the original Oasis song which sounds like nothing so much as the Oasis song heard while stuck in traffic waiting for a train. A good remix might be possible but that wasn't it. But like most things, the original is pretty darn cool and hard to top, although if Ryan Adams performed a serious version someday it might be a tough fight. Oasis may not have amounted to much despite all the hype, but for "Wonderwall" at least they deserve a couple of props.
Edited to add: Well, I tracked down the Beastie Boys cover, as well as an ever odder one by Metallica, although both are tinny-recorded live bootlegs and not very interesting. Also found a short cover by Radiohead that is actually quite good!