Speaking personally, I think in all honesty my life growing up, coming to terms with who I am, and dealing with that on a daily basis is probably far more selfish than transition could ever be. Because throughout all that time, I've been more focused on myself and how I feel - how everything in the world affects me and my internal sense of self - whether I want to be or not. It's just how things filter through my mind. Feeling different in your own skin causes you to question yourself, your relationships with others, how other people treat you is a reflection on who you are. For me it's something that's difficult to get away from because there aren't a whole lot of things that don't impact that in some way. And in that, I think I'm rather selfish for constantly assessing how I fit into the world, and how it fits in with me.
I've lost some dear friends and made some enemies because of the effects that not transitioning has caused, mostly because I think I've been wrapped up in myself, and sometimes the misery that dysphoria and the all pervading feeling of being different, and not myself has caused. I have not been so outgoing and perhaps not as friendly as I could have been. Distancing myself from people in need when I could have done something simply because I was too busy thinking about how bad I was feeling myself.
That, I think, is very selfish. And while I wish it were not the case, unfortunately it seemed unavoidable.
In answer to the question, I suppose it's a matter of perspective. My own view is that transition is, in large part, an attempt to actually be rid of quite so much selfishness by allowing oneself to be able to focus outwards for once, instead of inwards through dealing with the discomfort that not doing it causes. And in the long term, to aim to be able to be more unselfish towards others and in general.