While I don't really do much competitive stuff in video games, that does not mean that I do not have mains that I use. Some characters that I seem to use as mains in certain games are as follows:
Ares in Injustice Gods Among Us
Samus in the Smash Bros series
Deadpool in Marvel vs Capcom 3
Garland in the Dissidia games

The time sink required to get good is probably the biggest reason I've personally never dove seriously into competitive battling. The TCG is more my speed of competition and is a pretty big time-consumer to keep up with itself as it is.

Different people have different preferences. Some people prefer the competitive scene, where some just like to unwind and play more casually. Then there are the completionists who must do every single thing in a game (which seems ludicrous to me). Pokemon games can be short if you just play through the main story and beat the E4. However, there is a whole other world in Pokemon with competitive battling and breeding. These two things can take up a lot more time, there are people that do these for hours a day which only helps the franchise.

I remember when I first stumbled across the competitive battling scene in about 4th. grade. I had had Diamond for about a year and had beaten the game. I hadn't played the game for a few month when I stumbled across a Smogon-like site (or some other Nintendo/Pokmeon site I don't really remember) and started going into chats and trading and battling with others. As a kid it was an exciting time for me because it was like I discovered a new way to play the games that I had grown up enjoying. That's when I opened up and started playing Smash and other games competitively as well. I'm sure many others have had a similar experiences as well; it's great playing a great game with other exciting fans!

Binding of Isaac Rebirth is one of my favorite games by the way! Even in college me and a few friends will play the game late at night. It's such a hard game, and it was so worth it to finally be able to beat mega Satan after like 3 months of working up to it. Rogue-like games are some of my favorites! I believe that the harder the game, the more satisfied you'll feel after beating it. But maybe not, maybe it's how much you enjoy the game? I don't want to play a stupidly hard game, like Wings of V, in hopes of beating it. I'd way rather play through an easier game like Pokemon. However, Wings of V can be a nice alternative to play every once in a while when I'm looking for a challenge. I honestly think it just depends on the gamer.

I would just hit the like button but we don't have have that for blog posts so you get this **** post instead.

Hopefully when PCL starts up again I can help you out a bit with competitive battling stuff.....even though you might actually be better than me