So I've been playing SSBM for about 2 years now, and I want to find another game to play competitively. I've tried USF4, but I don't like it that much. I tried skullgirls, and absolutely love everything about it. The only problem is that there are no tournaments. Not that I don't want to play it, I just want to be able to watch (or even enter) the tournaments it has. Basically, what games play like Skullgirls, but have more tournaments. I'm thinking about Injustice, but I'm not sure if it plays like Skullgirls.
p.s. It has to be on PC
On PC your choices are rather limited right now. Japan's a bit behind on the PC scene right now, but they're slowly realizing the potential with its large userbase.
On PC, your options for fighters are that are the latest versions
USF4 and SG (which you already said)
Injustice (everyone moved onto MKX)
Mortal Kombat X (the PC port has issues and the online isn't very good)
King of Fighters XIII (game is losing activity)
Not a lot of choices unfortunately. If you're looking for something that will have big tourney scenes, USF4 and MKX are your best bet. Those are the two that are getting the most traction. Skullgirls is slowly growing, but it might take more time before you start seeing more of it outside of side tourneys at majors. KoF games actually do a good job on appealing to smashers due to movement options. You can always try this game on the side and see if you like it. The next game is being worked on, so you might be able to jump in on there.
Here's a list of pros and cons for 3 of them. Injustice isn't listed since the tourney scene has moved onto MKX. KoF, I just recommend trying out on the side before the new one (eventually) comes out.
USF4
+ PC has decent netcode now, lots of players
- It's not the type of game that you're enjoying
SG
+ Best game of the list if you want to improve through just netplay. Online is fantastic in this game
- Small pool of players offline
MKX
+ Game is new and a lot of people are playing it
- Bad netcode, PC port has some issues here and there. Still expensive