Hi there and welcome,
In my own experiences I will tell you I think you are going about this backwards. Trying to find things that he's good at, or enjoys are good for when he really gets a handle on his self esteem, but not foremost.
I can speak on this outright because I totally ruined the first half of my life dealing with self esteem issues. My parents had me in EVERYTHING - and I mean every day was practice for this, that, no free time hardly at all. One hand will tell you I've very well rounded in a multitude of events. The other will tell you, it did NOTHING for my self esteem. If anything it solidified by belief that I wasn't good any much of anything.
Self esteem isn't something that can be won as a prize. You can feel bad about your entire life and then win 1st prize in a handwriting contest and expect that to start the ball rolling. If anything - you remember vividly how well you did at few things because things we do good become habit - things we fail at become issues unless we have the coping skills to handle rejection.
My best advice to you at this point is put your money towards having him see a psychologist that specializes in cognitive behavior therapy. It's a little more intense that the typical "And how do you feel about that?" type. It will help your son get to the CORE issues of why he feels he's a failure, not good at anything. It took me years to realize that my self esteem did not really exist. Self confidence? Sure, but it's not the same as having the BELIEF that YOU ARE GOOD, YOU DESERVE TO BE TREATED WELL, YOU DESERVE THE BEST, YOU ARE SOMEONE TO BE PROUD OF.
-You aren't going to find those things out about yourself in ballet, baton, horseback riding, swimming, band, choir, ceramics, - You find self esteem by BELIEVING in yourself.
Sorry if this hurts anyones feelings, but it's the truth as I know it. There is a reason WHY he feels like this. For me I didn't even KNOW I had issues with being adopted. I could look you straight in the eye and let you know I had fantastic parents and opportunities like no other child - but in my subconscience - I was garbage that had been tossed out, unwanted by anyone. My mouth would tell you otherwise, my heart believed the words coming out of my mouth - but my psyche had a mind of it's own - really.
All told - it was the reason I picked the man I married, stayed with him through torturous abuse, accepted that same life for my child - and allowed whatever to happen to me - happen. I guess I convinced myself I was no good, and deserved it. Not true at all.
I am sorry for your little guy. It's tough, but I still think until he gets to the root of his self esteem - you're going to be waiting a long time for him to feel good about himself. He doesn't have the tools at his age to know how to fix what he has no idea is broken. -A psychiatric doctor. does.
Hugs
Star