Ouch. After playing all the Duke Nukem games from the original side-scrollers up to Duke Nukem 3D, I had high hopes for this game, a modern side-scroller. Boy, was I disappointed. The original Duke Nukem games were fantastic, incredibly fun side-scrolling shooters, but this game is a nearly unplayable stinker. Avoid this one- they shouldn't have done this to Duke, don't encourage more of it.
Tyrian is a fantastic game from the days of the vertical shoot-em-up. Back then, shareware games were common, and you could play the first full episode series for free without registering, and could share the shareware version freely, with anyone you thought might like it (I miss the golden age of shareware...) Anyway, not only did I defeat the shareware version multiple times, I also registered it, and played the full version through many times (quite a few things changed, even in Episode 1). I also purchased Tyrian 2000 on CD when it came out, and again, beat it many times over. The story, and the ability to purchase different ships, shields, and weaponry (each with multiple levels of power), makes this much more than the usual shmup. This is pre-bullet hell too, you can enjoy and explore (and the number and types of secrets are incredible), rather than memorize patterns. The only game I've found that is even close to Tyrian (and believe me, I keep looking!!) is Raptor: Call of the Shadows, which comes across like a rough early version of Tyrian's gameplay style. Give it a shot! Get Tyrian 2000 for that version, and get OpenTyrian for the original registered version of Tyrian!!