When will people learn not to dive like that...
Anyway strongest overall top... Generally, anyone who can do decent in lane and still make an impact mid game. Some champs require domination of a lane and a lot of feeding, like Riven and Rengar and the like. Others can just passive farm and do really well as long as they don't get forced out like Irelia and Singed.
I prefer the types that can get by on farm and still do well, as they have a more consistent performance. Sure, it's nice when you have Riven to a point that she can 1v5, but if she goes up against, say, a fairly decent Rumble who can keep up good harass and keep up in farm, he's going to have a lot bigger impact in those early team fights that will set the stage for the rest of the game, despite simply "going even" in lane.
There is no "strongest", however, as everyone has their counters or team comps that they do not belong in, and some champions playstyles/strengths work extremely well in certain ELO brackets but not so much in others, or they simply do not fit a team comp properly. Example: Teemo is a strong top lane vs many of the usual opponents, but if your team is relying on a top lane bruiser to be most of their tanking power and you're in lane against someone who can do extremely well against Teemo, then you just screwed the pooch pretty bad, despite how "good" he is.