Obama didn't so much win this election as Romney lost it. Romney was never a strong candidate--he never got 50% of the vote in the primaries except until the very end. He was an unconvincing campaigner.
But the surge he achieved after the first debate was telling: Obama behaved in the first debate as he has in office: detached, aloof, contemptuous, seemingly not caring about the outcome. A lot of '08 Obama supporters who've been disappointed in him showed their disappointment after that debate because they saw in his performance exactly what they'd been seeing for the past four years.
I wish Obama well in the next four years. I always wish our Presidents well--if they succeed, we all succeed. But, no President has ever done better in his second term than in his first term.