well, let's see:
Steve Brookstein - total pub singer, name is now synonymous with utter failure
Shayne Ward - had a few hits but soon became totally irrelevant
Leona Lewis - as stated.
Leon Jackson - see steve
Alexandra Burke - relatively successful in that she's now the most irritating purveyor of crap dance music in the uk, but she'll forever be a diet leona.
Joe McElderry - only notable thing this guy has done since winning is come out as gay.
Matt Cardle - too early to say, really. far from the worst winner though.
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And if you don't know, now you know.