One of my favorite NES games. Difficult as hell, don't let the vid fool you.
There are things you need to know. You have to collect 300 power stones to obtain full power. If you decide to power up through the game, it will probably take as long as 5 - 6 hours to finish it, if you know what you're doing. The easiest solution is to repeat the 1st stages with both Cpt. America and Hawkeye 9 times each, until you get those 300 power stones - the first 2 stages (cities) offer you 35 power stones. After that, everything becomes a lot easier, all you have to do is find the key crystals and complete each stage(city). It's not cheating 'cause this option can be found in the game. I've cut out the part where I'm powering up, as it was 12 - 15 minutes of pure boredom :) Enjoy!