I had the same problem. My depression had been latent since early HS but it really manifested when I began college, and my grades were horrible as a result despite having been a model student until then(well, until the last year of HS; college only hastened its development). I'm 29 and I've since gotten treatment but the effect on my professional development has been incredibly damaging. It's less a stumble out of the gate than a foot shot.
I know intellectually that I've achieved as much - or possibly more - than my typical peer because I've worked through my problems and traumas and come out the other end alive and healthy, but they're still the ones with the comparatively advanced careers, living in nicer cities, and taking care of their young families while I'm still working saw jobs in the midwest and living, alone, in a studio apartment.
But I'm alive, and I'm able to finally live a normal life, which is priceless.
Comparing yourself to others is an easy way to think negatively and possibly even descend into depression. It's important to accept who you are and what got you there and not think that your life would be so much better "if only things had been different". Things weren't different. You were given the genes you were given from parents who you didn't choose and countless other variables influenced you to become depressed and then recover at the time you did. No need to feel bad about it.
I don't mean for this to sound like a personal attack. I'm in a similar position to you and I've found it incredibly rewarding to realize that it is useless to worry about the past and what could have happened.
Cannot edit anymore, so what I wanted to say (I was not very clear) is : The lives they have is not necessarily as nice as you picture it, nor yours as bleak as you think. In the end, I would not really think too much (even if I know it's hard) about them. After all, they might had enormous advantage, or actually a shitty live, because everything is too perfect or maybe they struggled so much to be where they are and so, are exhausted intellectually and depressed.
You achieved an incredible feat by controlling your depression, I'd be proud of it.
I know intellectually that I've achieved as much - or possibly more - than my typical peer because I've worked through my problems and traumas and come out the other end alive and healthy, but they're still the ones with the comparatively advanced careers, living in nicer cities, and taking care of their young families while I'm still working saw jobs in the midwest and living, alone, in a studio apartment.
But I'm alive, and I'm able to finally live a normal life, which is priceless.