I ended up joining the Overwatch bandwagon too, got it after the last free weekend. I am still figuring out my favourites, just had a pretty good running playing as Ana. Usually I am in a healer in multiplayer games, but so far my highlights from each classification have been: Genji, Widowmaker, Reinhardt and a toss up between Ana and Zen-thingy-ma-bob.
The reason it's a toss up between those two is that I am actually not a brilliant sniper and do not play massive amounts of FPS games, though I am not a terrible shot, but being a healer sniper it kinda helps (the heal grenade and sleep also very nice). But Zenyatta (and the other healers) don't need me to be as accurate to heal. But Zenyatta I find to be slow moving and less interesting than Ana. But I can rock out his heals quite well most of the time.
Me and Reinhardt seemed to connect almost instantaneously, I tried it out when with a group of friends and was like "I'll just give it a go as we have no tank" and worked quite well in helping wreck the other team, killing their own Reinhardt multiple times 1 v 1.
Genji, the accuracy of the ninja stars can be a pain, but the mobility and the ability to dodge a lot is really nice, but the real nicely is the ability to deflect projectile attacks. I recall one match where I just continuously kept obliterating somebody's D.Va and for some reason I found myself able to cope with D.Va's better on Genji than other heroes.
Windowmaker, while, yes, I am not a brilliant sniper, I like that I can swap between sniper mode and semi-automatic and that I can easily get to vantage points (and get away) and utiliise the semi-automatic to shoot anybody who comes up closer.
As for Lucio, I am sorry, he's one I couldn't get along with.