Don't place a loyalty standard on yourself that is greater than the one being offered by Guy #1. He's not seeking anything else, so you're meeting a convenient need. By the same token, don't get yourself in an unfulfilling lapdog relationship with Guy #2...that could be equally unsatisfying.
I guess you really have to ask yourself whether you would be happy if the status quo with #1 was maintained for another 5 years? 10 years? Is this what you want or will you be feeling that your commitment is a bit unrequited by then?
I agree with everything Knott said (except the kiss)
If you don't grow where you're planted, you'll never BLOOM - Will Rogers