I'm not sure how I feel about this

[Forgotten22]

There's a guy I really like, but he really likes someone else.

In short, he took the plunge and asked her out and she recently rejected him. He was pretty upset about it and came to me for comfort, talking about how much he likes the woman and how upset he is that she's not interested.

A few days later he has asked me out.

It's upset me even though I've liked him for a while. It's clear how much he likes the the other woman. I feel like I want to say no?

You did the right thing. Relationships can convert from close friends to (good) lovers and partners but in my experience that is something that happens over the long haul. This is all a very short turnnaround. If he were really into you he would have jumped at the chance to deepen the relationship. I think, in a way, you called his bluff and he now knows if he were to date you it would have had to be pretty serious and he knows that isn’t what he wants right now.