These heroes are chosen based on my opinion, so in no way is this an official tier list.
McCree
I wasn’t sure McCree would make the list after his long range damage nerf, but being such an effective counter against Tracer and most tanks, he’s proven his worth. When McCree is close range with any opponent, he’s most likely to have the edge. He’s also very effective as a team player, being surrounded by supports like Mercy or tanks like Reinhardt. His effectiveness with a team is why he is so appealing to most competitive teams. Lastly his Ultimate called Deadeye has been extremely useful when his team needs a shift in momentum.
Mercy
Especially in the beta, I saw Mercy as one of the most selected heroes in Overwatch. Her ability to switch between healing and a damage boost are both admirable, but what really sets her apart is her ultimate called Resurrect.
Mercy can bring back a teammate fully healed from the dead, and in competitive play this ability is extremely over-powered. This can can give a numbers advantage to the team she’s on, easily changing the momentum of the battle. Not only that, but the power can also bring back multiple members of the team creating even a larger advantage. While she still has low health, she’s not easy to kill, being able to jump around from teammate to teammate.
Reinhardt
Some would say Winston is the best tank, but from what I saw in the early matches I watched, Reinhardt seemed to be a lot more effective. His shield is great for your team to fall behind and especially useful for countering an opponents ultimate ability, which in some situations can shift the tide of the match. Also with his ability Charge, he is capable of both poking the enemy, but also being able to one shot, some of the lower health heroes in the game. Reinhardt is looking more and more likely to becoming most teams go-to tank.
Widowmaker
The French assassin is the best defensive hero in the game. Being a pure sniper, you find a position, take a few shots at the enemy and use her Grappling Hook to change spots. Most snipers are poor with close combat, but with the combination of a close Venom Mine and her sniper switching to an average battle riffle, she can take down quite a few heroes.
Widowmaker’ss also one of the few heroes with additional options. In the options menu you can customize the aim sensitivity, which is appealing to competitive players. She does have some counters such as Winston and D.Va, but with a well timed grapple she shouldn’t have a problem avoiding them.
Lucio
In almost every recent match I’ve seen, the support has been Lucio. For starters he gives you a nifty speed boost at the start of every match, giving your team an edge right off the bat. Secondly, he creates an area of healing which is extremely useful when in the thick of combat. Most importantly, he’s such an appealing hero because unlike the other supports, he’s able to deal a good amount of damage.
Not having to have your team protect your support is huge but also it adds another attacker in the mix. Lastly, his ultimate move called Sound Barrier is extremely useful in giving your entire team a temporary health buff, which gives your team a huge advantage, usually leading to your team taking the lead.
Being so early in the games lifespan, it’s hard to say if these heroes will stay as relevant as they are now in competitive play, but if you’re looking to get into the competitive scene, these might be some of the heroes you’d want to check out.