The pick for Solo top depends on what champion you like the best...
For me, Gangplank or Garen is the best because of their farming abilities.
For range top users, Teemo and Vlad etc...
If you suit best for Melee and Burst damage, I suggest someone with quick combo, Talon is one pick. His burst damage is INSANE but has many counters.
Yorick is good against people like Riven, Olaf because of his Ghouls that can farm and damage like crazy from afar.
Garen is good for going head on. Silence and Spin deals a lot of damage that can dominate late game in teamfights, Same with Darius.
Renekton is one of the best solo tops but many players fail at using him because of his E. You just E to fight, deal ton of damage and use E to head out.
I have even tried Maze top solo and they aren't that bad... For people like Xin, Olaf, Irelia, they have ability to catch up in fights and leave you severely injured or can shut you down.
The most reliable thing for Solo tops are the junnglers, if the jungler is doing good, it should be no problem for you to dominate.
Every champion has a counter in the game, sometimes you try out a champion and you win 12 streak in a row and lose the 13th one, it might feel like you need to switch. Which is perfectly fine, there are many champions you can try and most of them may be common to what you like. Quick damage, Tankiness, Good escape moves with poking abilities.