Once upon a time when i was a young child in love with my NES ........
Finally that oversight has been amended. Not only can you unlock the original Contra (which I've never had the opportunity of playing) and Super Contra in this game, Contra 4 is an excellent game in itself. Yes, it's brutally hard at times. I see several reviewers complaining about this, so it needs to be addressed. As hard as it is, it's not really any more difficult than Super Contra, IMO. Anybody who knows anything about Contra should expect this kind of difficulty from a game with its legacy. People should be happy that they allow you to choose your difficulty (even though Easy doesn't let you play through all the levels). I appreciate the challenge, but if you don't want a game that you will die in A LOT then you shouldn't buy Contra 4.
One of the coolest additions is the Challenge Mode. You can unlock it by beating the main game on any difficulty. There are 40 challenges (many repeat the same concept, but occur in a different level) that require you to make it through levels with limited ammo, at a certain speed, not shooting any hostages, etc. The later challenges get extremely hard to the point that I thought some were impossible. I eventually succeeded, however, through practice. If you can beat the challenges you can beat the main game on Normal and Hard mode. Really I consider the challenges to be training for the main game on Normal and Hard difficulty. You will learn how to dodge enemies on the fly, destroy numerous enemies swarming you from all directions, and zoom through levels by finding shortcuts. This also adds plenty of extra play time to an already beefy game.
Multi player co-op is also an option, although I have yet to try it out. I don't know anybody with a copy so I am unable to enjoy the fun of blasting enemies with a friend. Also, one feature that I really like in Contra 4 is that you can carry 2 guns at a time (you switch between them with the L button), and if you get two of the same weapon it powers up (in Easy all guns come powered up).
Take the time to die a few hundred times and you will eventually become Rambo in this game. You'll be dodging bullets, blasting enemies, and making jumps like a pro. Satisfaction will fill your senses as you effortlessly flow through mind-numbingly difficult levels. What else would you want from a Contra game?