The thing about Homer is that he's good. He tries his hardest to do the right thing, all the time. OK, he's a moron, and OK, he's the greediest cartoon alive - but he loves his family, dammit. And that's important.
George Bush sr. famously said that he wanted Americans to be more like the Waltons and less like the Simpsons. What total crap: the Simpsons are much the better role models because they share the travails of us all. They get how difficult it is and they try their hardest and they fuck up occasionally but ultimately they're decent. They're devout christians, for fuck's sake. Homer is the best example of this: he's the one with the most to deal with - he's dumb, naturally selfish, greedy and short-tempered - but he always tries so hard. It's impossible not to adore him for that.
As well as all this over-intellectualizing bullshit, of course, he's also very, very funny. My favourite Homer moment: when he says 'don't worry about our financial worries! I'll sell my liver. I can get by on one!'
afterthought, which I'm putting here since I don't think it's really worth a wu of its own: as someone in The Guardian asked, could you ever really love someone who didn't like The Simpsons?