So I decided on which champions I'll main for ranked, but still not an AD Carry.

Ezreal
Graves
Kog'Maw
Vayne

These are the carries I play a lot, who do you guys think is "best"

Graves and Vayne are reliable and don't require as much support from your team as Kog does. Ezreal is best if you're making a poke comp, so keep him around for when you want to be mobile and have that great ult.

I once sniped a lee sin from across the map. I was trying to steal dragon which was long gone (didn't have wards at the time) but the ult traveled to the purple team's golems and I killed lee sin. Obviously planned :3

Graves is safest pick , easy to do well with and is not weak at any point in the game.

Graves is stupidly OP. He's a 'short range infighter' that can toss down 3 AoE nukes at 750 range (greater than pretty much anyone else), 2 of which scale really well. He's almost a physical caster..has a super annoying Smokescreen..and has an escape on top of that.
The pros still prefer Kog slightly (though 80% of the games have a Graves), due to his longer range. But their teams also know how to protect Kog to take advantage of his range too. Not so much in solo queue... so I'd prefer Graves.