The Batman games already look pretty decent once you bump all the settings up and engage in a bit of downsampling. But it's nowhere close to as good as what modders can do.
It's a massive undertaking from GP-Unity, who is a fortnight away from releasing a texture pack and graphics mod for Batman: Arkham Asylum. And while that game already looks pretty solid as-is, it gets a whole lot better with lighting tweaks, increased reflections, better shaders, the removal of that nasty green tint, improved shadows, updated textures and an overall regrading of the game's colour.
The full mod won't be released until December 20 (likely December 21 our time), with more textures to be updated before then. There's instructions in the video description if you want to try out a beta version of the mod, but be warned: it's a lengthy, convoluted process.
But if you'd like to play Arkham Asylum with it looking a little more conventional and vibrant, this is a decent solution. Aren't mods great?