Originally Posted by CountChocula 
I've never played Halo or COD, but aren't the single player campaigns for those games also pretty short?
My son beat black ops in less than 3 hours. I beat spec ops the line in about 7 and fear 1 in 7-9 IIRC it was a while ago.
So even at its shortest its not too bad in comparison.
For me 20-30 hrs. Is fine nowadays. I don't finish many games if they are longer because I don't have enough time. If its to long I find myself playing for a while then getting too busy and when I get back to it I typically start over because I forgot what was really going on.
I played the first 20 or so hours of DAO 4 times before I got enough uninterrupted time to play it threw. That's a game I really liked though many other game I find myself never getting back to.