It depends greatly on both personal preference and what android device you are talking about. There are some mediocre android phones out there, but models like the Samsung Galaxy S, and Motorola Droid are more or less on par with the iPhone 4 (a bit better at some things, a bit worse at others) and I think the HTC Evo is slightly, but clearly superior to the iPhone 4.
Android phones offer far more choice of size, keyboards, specifications, etc. iPhones, on the other hand, are a simpler and reliable choice for those who don’t really much about smartphones and have no desire to do hours of research.
In the long run, I think the better android phones will be better than iPhones. With so many manufacturers competing to put out better and more innovative android phones, it will be hard for Apple to keep up.
All of the android phones are imitations of the original iPhone. As the android platform splinters among carriers with different hardware, none of them will be able to keep up with the quality of the iPhone.