Double Dragon is certainly a difficult game, full of tricky moments that can see you killed in a few seconds, but if you have the Jedi skills required to persevere then you'll enjoy what is arguably the best conversion of the classic arcade game. The game is for one or two players but sadly you'll have to take turns if you're playing the main game.
One of the odder things about this NES version is how you have to gain experience points to be able to do the more powerful moves. So early on in the game it's actually beneficial to try and keep enemies alive for as long as possible by hitting them then running away before you deliver a finishing blow. Its kind of an annoyance that you have to do this, especially as it means you don't start out with the ability to jump kick but if you really hate it that much there's a glitch in the second level which allows you to cheat your way to as many experience points as you want.
This being a NES game controls are simple, and the special moves you learn along the way can all be performed quite easily (most of them just happen automatically). Despite it's age Double Dragon is still better then most side scrolling beat-em-ups. The joy of smashing a bad guy in the face with your knee and then sending him careening over your shoulder remains as glorious as it was in 1988. Less glorious are the jumping sections that require you to press two buttons at once to jump, which can lead to many a frustrating death, but after a few mistimed leaps, you should get your head around the slightly weird jumping mechanics needed for these areas.
The one major problem with Double Dragon is the fact that you're only given three lives to complete the game. If you have the patience to learn from your mistakes then a grueling but just about fair challenge awaits you. However if the thought of having to constantly restart from the very beginning of the game doesn't sound appealing to you, then this isn't the game for you.
If you feel up to the challenge then Double Dragon is an adrenalin soaked glee-ride. No matter how unfair a death, no matter how many times a boss has bettered you, it's such an inexplicably enjoyable title that you'll likely find it difficult to resist having another go at it. It's tough as old boots but also an awful lot of fun. Double Dragon looks, sounds and plays phenomenally well for a mid-generation NES game.
If you fancy a change from the main game there is also a one on one fighting mode where you can beat up the computer or a friend. Obviously this mode is hardly on a par with Street Fighter 2 (both fighters must always use the same character) but it's a nice bonus all the same. All in all Double Dragon is still one of, if not THE best beat-em-up on the NES.
It's rock hard though I've owned the original NES cartridge since 1991 and I've never beaten the final boss!