fine... and that's ALL? Just fine? At age 25, you are considering perpetuating a relationship where sex is only fine?

I also agree with everything Rose said. You are afraid of hurting him by leaving now but you will eventually hurt him much more if you drag it out and still end up leaving later as you undoubtedly will.

But you do want to protect his feelings and I think he will be hurt less if you explain that the relationship has become, as said above, lackluster, that you cannot put up with his lack of any passion, drive, creative pursuits, or interests outside video games, THAN if you bring up that other guy who currently excites you so much.