As I was holding my family's place in a long line over the holidays (note 1), I took the opportunity to look at the 20 largest U.S. retail banks through my iPhone. They are all passable as long as you are willing to take the time to zoom in and navigate with your finger on the touchscreen. 

The best-looking sites are those with relatively simple hompage designs, notably ING Direct and HSBC and to a lesser extent Wells Fargo. But the hands-down winner is Bank of America, the only top-20 U.S. bank with an iPhone-optimized homepage.

This provides BofA with several short-term advantages:

• Bragging rights as the first major bank to design for the iPhone
• A spot on Apple's directory of Web apps for iPhone (here) (screenshot below)  
• Several mentions in tech and personal finance blogs
• An entree to the 1.4 million, decidedly upscale, iPhone users

Note:

1. Survey of 20 largest U.S retail banks, by deposit size, made at 4 PM on Dec. 24 from Seattle IP address through iPhone browser on AT&T Edge network.