You're right about the popularity contest thing. But to suspend disbelief for a minute or two (because this kind of speculation is fun):-
I'd always assumed that Lobo's heart just wasn't really in that fight. He was being forced to participate and he never does anything he doesn't want to do. Was he drunk, too? He killed off his entire home planet, I'm not sure he cared as much as Wolvie about the universe vs. universe struggle.
Wolverine had more to fight for - and he didn't have to kill Lobo, just immobilise him. I know Lobo's fought Superman, but has he really never been knocked out in a bar fight before?