I wouldn't completely write off Coldplay. I think X&Y and Chris Martins shifting personality have damaged them significantly, but try and remember pre-X&Y, pre-Chris Martin acting like a tool at every opportunity. Parachutes was a killer debut. Rush of Blood was a 'big'/expansive second album. Few individual songs have caused such a meltdown here as when Clocks first appeared, overplayed as it is, don't pretend that you've never liked it. Then, he starts acting like a moron. Then comes X&Y, an album that had a stench so bad it infected Rush of Blood as well. It was so similar, but so bad, it's effected everyone's opinions of Rush as well.
They're forever compared to U2, but really I think the only true similarity is their ambition. Like U2 they want to be fucking massive, hold a position beyond just music, and they're not afraid to make that obvious. Perhaps also like U2 their lead singer is polarising, but I think the public opinion of Martin probably swings further into purely 'dickhead' territory than it did for Bono so early on.
Wanky name dropping: I spent a day with Coldplay just before they went truly massive. Just as Yellow hit. They were easy going, fun guys. Chris Martin was really laid back and nice, very inquisitive guy. My guess is that like Bono in the 80s, he's putting up a public persona that doesn't tell the whole story of the personality. He's just not very good at it. He doesn't come off like an earnest tool like Bono did, he comes off as an egotistical tool, a problem that Bono has always danced around and defended against with self-depreciating humour, but Chris Martin just seems to continually crash into head on.
Point being: Somewhere in there they probably still have a shot, but they've done their 'U2' run all in the wrong order. Post Parachutes and Rush of Blood a lot of people thought their Joshua Tree was just around the corner. But they jumped forward and released their own Atomic Bomb stinker. And now they need their Achtung Baby - tear it all down and build it all up again, and make it dramatically different. They were a parody of themselves on X&Y. There are 5 or 6 absolutely brilliant Coldplay songs on their first couple of albums, and I'd rather them out there than a lot of the other shit that sells as much as they do and has a profile as high or higher than they do. He just needs a wake up, and they just need a musical reset.