You said:
Im not disagreeing they are better top or whatever but I love playing these champs mid because its more of a challenge on my alt account and FAKER (league gods) knows I need the Practice. Opinions on it? I got to s1 with riven/fiora mid and I have a g5/4 MMR
I don't care if a champion is meta or not, but ask yourself this. Are you playing Riven mid because she has potential there that you're trying to capitalize on or are you playing Riven mid because it's more challenging? If Riven mid works and your teammates are just blindly following the meta, then it's your team and not you. However, if you're playing Riven mid because you find it "more challenging", then I'm going to have to say that you're at fault.
It is selfish to jeopardize the win potential of four other people, some of whom may be playing their only game for the day and just want to get their first win, so that you can practice and enjoy a challenge. What if your jungler decided to play AD Morgana jungle just because he found it challenging on his ult account. Would you find it fair losing because some smurf was trolling in your game?
Off meta picks are fine, and some games you need to just ignore your team and do your own job to the best of your ability, but never put showing off above winning.