Most Helpful Guy
There's no nice way… either way he'll feel hurt, it sucks isn't it? Just be as gentle as you can and understand him… although sadly there's a big probability exactly because of that is that he likes you, for not being a bitch but a nice and humble women, unfortunately there are not a lot like you, by the way, maybe you should give him a chance, some thing similar happened with one of my exs she had a crush I didn't felt the same way and at the end that had been my longest relationships so far, you might get surprised 😉
Most Helpful Girl
You just have to be honest. It's possible to be truthful about these things without being harsh. Of course, you should understand that rejection always hurts so even if you are nice about it he will probably still be upset. Unfortunately, that can't really be avoided in situations like this, but you should still be as straightforward with him as possible.
You can tell him that while you are flattered, you just don't feel the same way about him and would prefer to remain friends. You should also not accept the gifts or if you have already, give them back to him. If he tries to argue or attempts to talk you into it more, then it's okay to be more firm and tell him, "No, I'm sorry, but it's not going to happen." It's important to be straight to the point and not leave any room for false hopes about the future.
Just so you know though, it's possible that he may not want to continue being friends, or at least not close friends, after this and that's okay. After being rejected, some people just want distance so you should prepare yourself for that, in case that is how he feels.