Tim Drake and Dick Grayson are the only ones who can really be considered lol. Tim Drake's the best Robin in terms of Batman and Robin as a team, because he was written in the right time for the character to stand out and he definitely earned the name time and again. Because of the tragedy that is Jason Todd, Tim received more training and was kept close to the Bat at first to make sure he'd be 100% ready for anything he'd face out there. Because of the glory that is Dick Grayson, Tim wasn't held too close for long and was eventually given his own breathing room after he'd proven himself. This allowed him the chance to go on more of his own adventures than the previous Robin's did. Tim is the Robin he is because of how Bruce handled his first two sons. He learned from the mistakes he made with both and was careful to treat Tim with all the respect he deserved.
Dick Grayson's the best Robin in terms of being a hero, you only have to read the New Teen Titans era to understand that. Back when Dick was being written as Robin alongside Bruce he wasn't given much personality and didn't have many solo adventures. It wasn't until the New Teen Titans where he really started to shine on his own. That's why he isn't the best Robin in terms of Robin being in Gotham with Batman. His best days were never in Gotham. They were out of Gotham with the Teen Titans. Which is one of the reasons he's the best hero for the world out of the Robin's. He's had a bigger impact on the superhero community than Tim or the others by being a founding member of the Teen Titans, and pretty much the overall leader (Like in Young Justice) Not only did he do good work with the Titans, but he formed a legendary team that would set the standard for years to come, and made it so that the concept would be emulated by future young heroes. Giving them a place to meet, train, and work alongside others their own age, with similar problems.
Dick Grayson simply wasn't Robin during the right era. Re-create him in the comic world of today and it'd be a different story, but as things stand Tim takes the title of best Robin, with Dick a close second.
Just to clarify, are you saying that Tim is the best Robin to work alongside Batman due to circumstance?