The game was great for it's epoch, however cannot match today's games (but all action games are like that.....they loose value too fast). I used to play it when i was a kid, it's a good game to spend a few hours before getting bored of the repetivity and it has the unique feature (for the time) to buy stuff and upgrade ur spaceship. Overall it's a nice game to have as a classic.
If i was about to rate it in 89 when it was released i would give it a 4.2 for good graphics and smoothness and those extra features that other games lacked not five though because it is not a unique idea....by my opinion it's an enhanced space invaders version. Today though if i would compare the overall value against other old games, especially adventure one's it cannot stand chance. However if i compare it with same genre kind of games it would still score high
If you like flight fighting games go for Red Baron, which is also around the same age
Xenon 2 is a great game for kids mostly.