Whether or not he deserves any credit - and he certainly deserves a lot of credit for some bad things - what I think has been lost is the fact that the latter half of the Clinton years were good times. Good times in a way that that hadn't been experienced since the late 60s or so. I don't just mean in terms of purely quantifiable things - though the numbers there are good - it was also the case that there was a real sense of optimism. America, we're back, bitches! It wasn't all a horror story in the previous couple decades, but "morning in America" ads aside, there was a feeling of stagnation.
Dems have plenty of reasons to be mad at Bill Clinton, but for those wondering why there's fondness - it's because the economy boomed and he ultimately kicked their asses.