The best phone cameras (iPhone, Droid) are pretty good, but not nearly as good as a good compact camera, and nowhere near a DSLR.
The best phone GPS's are very accurate, but have nowhere near the battery life, sensitivity, and ruggedness of a Garmin Legend unit designed for hiking.
The best phone keyboards are quite usable, but not as good as a tiny netbook, and nowhere near a larger netbook.
The best phone screens are large and clear, but not nearly as good as a portable DVD player, and nowhere near a notebook.
The best phone processors (ARM Cortex A8) are pretty darn close to a netbook, but nowhere near as powerful as a higher-end notebook or desktop.
The best phone media players (iPhone) are... okay, a decent phone actually is just as good, if not better than, a dedicated MP3 player in this case.
When you have a good signal, a 3G connection can give pretty high throughput, but not as good as midrange DSL or cable connection, and nowhere near as good as most universities' or corporate offices' bandwidth. ... And everyone seems to like it that way. The smartphone seems to have become the jack-of-all-trades device, highly integrated and packing tons of features. The best ones are good at lots of things, but they're not really "the best possible device" for any one task. Smartphones are good for talking and sending messages and browsing the web and figuring out where you are and taking photos and playing music, but there are dedicated devices that do any thing better. This probably explains why there's no phone that's just amazing for gaming. It would compromise all the other functions to a degree that would render it attractive only to a niche market.