I don't find that games are getting shorter really... but it largely depends on if you are willing to go into the extra hoops the game devs have put into the game.
For example, Shadow of the Colossus, great game, if you play it once on one difficulty, 5-10hrs tops depending on how good you are at figuring the bosses. If you had fun trying the hard mode or the time trials, you just tripled the play time easily.
If you want to stretch the mileage of a lot of games, try achievement/trophy hunting.