What you are feeling is the direct result of a mistaken notion that your sin is less heinous than someone else’s, so you deserve God’s forgiveness while they don’t. The hard reality is that you don’t deserve it either.
I think there's biblical justification for the idea that apart from being in Christ, the consequences of various sins are ultimately the same (though that may be more nuanced due to the possibility of degrees of punishment) as well as the idea that no one deserves forgiveness. What's far less clear to me is the basis of the oft-repeated claim that all sins are equally severe or equally heinous. No one is going to make it to heaven by sinning less than the other guy, but still, it seems that there are clear differences. Different sins can violate God's perfect standard of justice and his good order of creation (what's left of it in the fallen world) to differing extents. Also, I would suspect that (to take a rather extreme example) a cold-blooded murder is going to do (at least on average) more spiritual damage to the perpetrator than flipping the bird to someone in traffic, even though both may qualify as sins.
I think this is rather comparable to a situation where people are trying to jump over Grand Canyon and some jump only a yard or two where someone else might be able to make a new long jump record and jump 10 yards into the canyon. It won't make a difference for the outcome, but clearly they're still not the same.