What do you do when you have a great potential co-founder, but don't like their idea?

I have friends who are smart and talented and would make good potential co-founders. And they want to work together. But often the idea they want to work on isn't right. Either:

1) I feel they're thinking too small. They're incredibly talented people, but they want to pursue what I think is a really small market, and could be doing something more worthy of them.

2) We have different opinions on the business prospects for the idea - I think it's just OK, they think it's amazing.

3) The idea seems boring to work on, often because the idea is 95% marketing or content and not technology (e.g. a variant on an online store, blog, content site, etc.) This is bad for motivation.

I have good ideas of my own, but it's hard to persuade people to change their mind once they've decided what they want to work on. Since I'm not in school, I've had to work hard to find other good people (through a lot of networking) and it would be a shame not to do something with them, So, should I move on and look for someone to buy into my own ideas, or start working with these talented friends of mine and hope to evolve their idea into something better?