Marvel's Avengers, the superhero smash-'em-up game from Crystal Dynamics and Square Enix, has become a daily play for me. But that doesn't mean it's for everyone. For casual players out there, the early hype surrounding the release might have been enough to check it out during August's Beta release, but even the hardcore players are starting to drift away from the relatively new title. That's a problem for a few reasons: First, with a dwindling player base, it's going to be hard for the game studios to greenlight additional updates in the …