Tap is usually the best, some bottles are pretty good, cans (with a few exceptions like the nitrogen bladder Guinness can) usually a distant third. I haven't had enough of the new spun aluminum bottles to reach a decision yet.
There's nothing inherently bad about beer in a can. In fact, some respected breweries are putting their best product in cans. It protects the product against light much better and cools faster. The main issue was that most beer sold in cans were cheap beers. Also - drinking straight out of a can does lead to a "metallic" feel that isn't there once it's poured into a cup.