Genres you were bad in but grew better

Bullet Hell in general.

I used to credit feed my way through Gigawings as a kid, but now, with Touhou I can pretty reliably beat it while using only one continue on normal. With the exception of Mountain of Faith and Subterranean Animism, because screw those games.

Racing Games

FP Ss. The best I could do in call of duty world at war was kill with the M1's grenade launcher. In MW 3 I'm half way decent with a machine gun, and pretty good with the M-16.

I used to be pretty bad at action games until I specifically sought out the Devil May Cry series to improve myself. Still not awesome, but I consider myself to be reasonably competent now.

Realistically speaking, I guess you could say any genre for me, seeing as I started playing video games when I was six. I was decent enough with racers and platformers, but I was really terrible when it came to fighters and RPGs. It wasn't until I was about 12-13 that everything came into place. In the latter, I learned more clever strategies instead of Attack! Attack! Attack!, item management, team management (skills allocation and how to specialize when leveling up units), and whatnot. In the former, I actually learned how to pull off moves instead of Button Mashing and hoping I could get a "SHINRYUKEN!" and experimented to see which characters fit my style and what combos worked best in x situation(s). I'm actually now a pretty good contender when it comes to games like Street Fighter, Tekken, the Vs. games, Soulcalibur, Smash Bros., etc. as my friends can attest to.

I used to be unable to play any sort of FPS with controller, and needed a mouse or at least a wii remote to control my aim. But today, due to the miracles of way to many video games, I am able to play Nazi Zombies with the best of them!

I was horrible at fighting games but I actually got the hang of D-Pad rotations after picking up Gundam Battle Assault 2. Haven't played a console fighter since, though.

I god moded my way through Mechwarrior Mercenaries but I became relatively good in the 3rd and 4th main games.

Count me into the "used to shamelessly creditfeed shmups" club.

Rhythm games. Though, I suppose everyone was bad at it in some point of their life.

STGs (Shmups) are my primary contender. At first, I'm not making any progress. However, I have to improve a lot so that I can get some progress. I rarely credit feed, since I'm more of a guy who tries to complete the entire game with one credit.

Also, Devil May Cry. I can't count how many times I got killed the first time I played this game, but after learning the ropes of this game, I'm doing pretty good.

Like everyone else, Team Fortress 2 and other FPS. Also, fighting games courtesy of Soul Calibur.

I used to be piss poor at RPGs, until I learned the value of all-party stat buffs and debuffs in Mother 3.