Airbus sees a market for super jumbo jets to serve high density routes. Boeing sees a market for smaller (but not small, the 787 will carry over 200 passengers) that can operate with great flexibility and efficiency.

I suspect there is a market for both planes. I also suspect that Boeing will sell more 787s than Airbus does the A380, but since the A380 costs so much more, that's pretty much a no brainer. The A380 won't be able to serve as many airports as the 787 due to infrastructure requirements or market demand. I think it'd make a great cargo plane and that's a rapidly growing market segment.