I'd never call it a great game, but I can enjoy an occasional round of Space Attack. If actually you're trying to win, it can get interesting for a while (but with practice, yeah, it eventually gets too easy.) I'd actually rather play it than Atari's 2600 Star Raiders, but yeah, pretty much any of the other 2600 starfighter games are superior.
I'm not sure the primary reason for M Network was to lure Atari owners over to Intellivision (although, I'm sure they wouldn't have minded that outcome!) More likely, it was just to make money by porting their games over to the more popular platform. It's not like all M Network games were inferior to the Intellivision versions after all, but you know that, having given glowing reviews to Lock n Chase, Astroblast, and Dark Cavern.