I'm decent enough to avoid embarrassing myself in most genres, but have no real strengths either.

I'm good at CS:GO and decent at FIFA 14.

Out of 10 I would give myself a 7 on how good I am.

idk. i'm stuck on candy crush.

Well after 35+ years playing games I'm very good I would say, but there are games I'm not that good at. Chess on ZX Spectrum for example :) No but FPS games is something I'm mediocre at and games like FIFA, but I'm a bit of a professional 2D Mario player. I can beat Ice Climber all 32 stages without dying also..done it many times.

I consider myself very skilled at platformers in general, but if I put enough time into a game I can be very good in any genre. I used to speedrun games that I really liked, so I consider myself very very good at a game when put the effort and time in learning it.

Except for fighting games that are not Smash....I suck real hard on those.

I set my first national(Italian) record when I was 15 years old, Mattel Intellivision, Beam Rider.  I think you are a great player when you play games in a way most can't or you do records that most can only dream. Many players simply can't finish KillZone2 at Veteran or Elite. So, if you do it, sure you are a very good player.  Also MP often show the level of a player, your shooting skills, your team work, strategy, maturity, ability to keep a cool head when the majority lose control in the most critical moments, etc. Generally your friends are witnesses of your skills. If all friends consider you a God at Uncharted3 MP, for example, sure you are a very good player.  

I was a God at Uncharted2/3 Coop MP, at least all my friends call me like this.  I really love Uncharted coop.

I am great at my favorite genres (MOBAs, RPGs, and Platforming) I consider myself above average in my gaming skills and I am quick to adapt but I am not good at all at FPS and strategy games.

When I beat Rol in Mario Kart 8 then you all will know.

i can find myself beating any type of games if i put the neccesary time on it and that's enough for me to enjoy games without getting frustrated.