This is how to make shootemup games!
I was not very fond this genre, because I looked at the wrong games. Most of these (even if they have good graphics/music and a working collision detection) are mindless, boring, repetitive, impossibly hard, and very, VERY frustrating. This was one of the most popular genres in the 80's, but it looks like they missed the point most of the time.
And there is Gradius, from Konami. They took Scramble (another great game of theirs) and improved it. They added a power-up system, among many other new features. I don't know what is the arcade original like, but the MSX port of is very well done.
Technical wise it is as good, as the hardware of the MSX 1 allows it. Yes, the C64 version has a rich sounding music, colorful sprites, and smoother scrolling, but they left many details out and cut many corners, so in overall, the MSX version is better. Indeed the music is something that will stuck in your head and you will keep humming it, especially the tune of the first level. The MSX even has sound effects and music simultaneously, plus it has all the soundtracks from the arcade. The collision detection is also forgiving (another minus at the C64).
The level design looks inspired, with each of it's own set of enemies (Moai statues, anyone?) The bosses are the same, but immediately before them are so called "boss-rushes"
where you have to survive intense perils unique to each level. The game is quite hard, but not impossible! Checkpoints are scarce, but fortunately, if you loose all your lives, you can continue from the last checkpoint again, in case you press F5 in time. I like this! This feature keeps me want to continue and does not make me frustrated, because I lost all progress (sadly, this is missing in the C64 version.) Due to the power up system, you have to involve a little bit of tactics if you want to have the right weapons at the right time. When you die, you loose all the upgrades. I noticed that the developers placed the checkpoints that way you can collect just enough upgrades you will need at the end of the level. This is not obvious at the first few try, but as you find out the right path and right timing, you will succeed!
I can't think of a problem in the MSX version. The C64, ZX Spectrum, and Amstrad CPC versions are not as good ports as this, but I don't want to talk about them right now.
The Bottom Line
Those Japs really know how to make fun shootemups!
Although Gradius was revolutionary at the time. there were made a lot of improved sequels and other games in the genre (like R-Type, aka "the ultimate shootemup of the 80's").
But if this is dated, the majority of the genre is COMPLETELY obsolete!