I don't think "average" means "game I found okay". I think it means "incredibly common place". Insipid, if you will.
That being the case, The Orange Box and Canabalt are most certainly not "average" games in my opinion. In fact, those two games beat the crap out of convention pretty bad. I think it's rather intuitive and that there has been nothing quite like it before.
In my opinion, the most commonplace game would probably be any game made by Bioware post-Kotor. The same damn action gameplay coupled with an encyclopedia's worth of text in dialogue boxes. Couple that with the karma meter and you have an experience as intuitive as taking 5 personality quizzes on facebook, then playing a stupid flash game.
I don't think dialogue boxes are particularly bad, but I've seen games who have done them better like Deus Ex. Games that understand the subjectivity of morality and create long-term consequences more complex than "It makes me feel safer knowing you're around."
Speaking of which, Fallout 3 gets spared from this title because at least they took the time to come up with a genuinely charming aesthetic that drove me to explore more of the world than I otherwise would.
So yeah, that's the gist of it. There' still a multitude of first-person shooters, fighting games, and other genre archetypes to tackle, but the Bioware game model is just so much more boring and tedious.