I didn't really like Contra 4, so yeah. I've never played Neo Contra or Shatter Soldier either.
I really like this game, but I do have a couple problems with it. For one, it's WAY TOO LONG. I mean this game will take at least an hour and a half to clear, which is pretty crazy. I can just imagine how pissed I'd be getting game over'd on the true last boss when playing arcade mode. But thankfully you can practice everything in Rising mode, so there's no real reason to play Arcade until you are confident you can clear the game.
And secondly, there are some control issues. The main problem is how "sticky" the grabbing is. Like sometimes you'll be trying to jump over a pillar before you get pushed off the side of the screen and lose a life, but you'll keep grabbing onto the side of it over and over before finally making it over the top. And the other control issue that kinda bugs me is that it seems like animation gets in the way when you're trying to turn around quickly and go prone. It doesn't seem instant like in previous games. But maybe that's just my fault.
But other than that, it's great. Challenging, excellent presentation, lots of variety, good boss fights (for the most part), lots of power ups to unlock, etc. Well worth the $15.