Devs develop for phones. Until Android 3.0, there has not been a big push for development for tablets specifically. Right now games on Android is more of a weird combination than anything else.
Touchscreen based gaming works, and sells. iPhone and iPad are examples of this. But is this serious gaming? It depends on what you mean by that. Probably not.
I do not think Android tablets will ever be able to match the experience of gaming on dedicated platforms.
Fragmentation already screws many Android devices on the market. I do not think tablets will reach the same level of gaming experience as dedicated gaming platforms. There is the issue of distribution, support for multiple devices, and software piracy on Android.