That's what I think, too. The first person you're with will always be etched into your mind. That's true for everyone. And I imagine that the longer it takes to find someone, the higher your expectations that it will be THE one, so you kind of put a pedestal under that relationship. It's likely that she had a bit more experience, so it didn't affect her as dramatically as it did you, thus the tapering off of her interest. She was probably expecting something more casual and your intensity (I'm assuming, since it's only natural for a first relationship) might have had her feeling kind of smothered.
It's interesting that your second relationship lasted longer, but not at all surprising that it didn't work out, because rebounds rarely do. You're always really looking to get back that feeling you had with the first one, so the new one can't help but fall short of that idealized romance.
Not to pry, but why the late start? Knowing that might give more clues as to the direction that would help you the most now... And what do you do for a living? Do you meet many people at or through work? You know, for a lot of people who are slow to get around to dating, match-making resources are often a good fit, since you don't have to sift through so many random unknowns to get to the kind of person you're looking for. Late bloomers almost always have a pretty good idea of what they want out of life for themselves, and that works in your favor in selecting a mate that fits your personality and goals
As far as your memories of your first love, you don't have to let those go to move on. You just have to memorialize it as a part of your past and realize that you can only move to the future and live in the present. I'm sure that after two years you've done all the analyzing and second-guessing possible, so any information you have gleaned from the analysis is all you're going to get, at least from your own perspective.
Rather than dating a bunch of women casually (I just don't see that being "you"), why not get a pet to share your home and your life to take some of the pressure off of seeking companionship? Plus, they're chick magnets
Best of luck in all your endeavors.

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