Repeats itself a infinitely.
Women leave great guys because they're not as exciting as the "bad boy", complain that he cheats on them,doesn't respect them, etc.
And 5 or 10 years later come on here and complain that there's "no good men" around.
You have them,and most of the time you push them away.

Except I'm a guy and the "bad girl" seemed more exciting than my great girlfriend. -OP

I feel you my friend. I stand conflicted as well. It’s hard to know what really could have been.
Also, maybe she’s not all that bad of a girl and could be perfect for you?
Who’s to say?

You're with someone who should be ideal and yet you spent the last decade in regret and dissatisfied, which doesn't sound like the right choice at all. You're also still thinking about someone else you talked yourself out of being with for a whole decade yet you never spent the time with them to see if they really were the wrong choice you label them to be, and that person is still on your mind after all this time.
Sounds like you were trying to be clever and strategic in picking logic over the heart, and the heart knows what makes it happy. More people would be better off if they actually listened to their heart from the onset.
Too bad you didn't get the memo, huh?

This is a silly thing to post. Had you gone for the wrong girl and ditched your girlfriend, you would have been even more miserable now, being alone and knowing it's because you had given up something good for no reason.

Don't beat yourself up for listening to your instincts.