Loch Ness Monsters is quite a good game. I'm not sure of another game like this on another platform() It's on a Rhetoric disk if you fancy a play.
Acheron's was an OK shoot-em-up. I found the controls a bit tricky. Anything too complicated gets in the way of the fun - but you can use the odd controls to strategically place your ship and sit waiting for to blast the enemy. A bit of fun. But after a few screens you can get a bit bored with it.
Loki remains a crazy mad shooter which can keep your attention longer - if you get the hand of avoiding the ships/ missiles/ rocks.
So I think I'd give Loki and Loch Ness Monsters a 5 with 4 for the others. Galaxy 5 should maybe get a 3 but there's 5 games and a couple of them are not bad. I used to read through the BASIC listings to try and learn something about programming. I tweaked the progs a few times but forgot to save them. I probably didn't have a spare blank tape in those days! Times were hard !!!