This is mostly my personal experience, so others may disagree with my points.
Top Lane - I find Irelia and Maokai are pretty consistent winners at the moment. They both do well against ranged and squishy top laners, they have sustain to survive lane, they both get tanky and have good innate damage, and they can easily set up ganks for their allies.
Ryze also wins lane consistently against more melee champions and scales very well.
Mid Lane - I find Morgana and Lissandra do well. They have a lot of CC for utility, good waveclear and roaming, some form of sustain in lane, strong AoE damage and CC to change teamfights, and pretty safe matchups.
ADC - Ashe is probably my most consistent, since her definition of winning lane is going even. Her ultimate can easily set up ganks or help other lanes (landing an ult on an enemy Yasuo as they ult your mid laner is hilarious), she has good short trades (CritAA, Volley, AA), a permanant slow so enemies can't escape when ahead, and is good at kiting teams with volley.
Another good ADC would be Corki. His Q and ult make safe trades easy, he does a lot of mixed damage, safe waveclear, and a good mobility tool.
Jungle - I like Amumu, Maokai and occasionally Gragas. They have good farming and ganking ability, so you don't fall behind if all of you lanes push. They can get pretty tanky while still dealing noticable damage (percent max health and good bases) and serve as good initiators and disruptors in fights.
Keep in mind that most of my champions are durable and/or utility picks. I find that my teammates often chose squishy damage dealers (assassins, burst mages, carries) and that we lack CC or tanks, so I try to make up for it. Also, my definition of winning a lane is typically surviving the lane or getting ahead as a champion who outscales their opponent later in the game.