I don't think Alien Breed was anywhere near as difficult as it's close relative Project-X was. Wasn't there an option to set the difficulty level? If I remember correctly, the only 'unplayable' setting was the highest one. Main thing about this series is that it's a total, shameless rip-off of the Alien film series, of that wonderful Sega game, Alien Syndrome
(just love that game
) and probably lot's of other stuff too. Team 17 wasn't about originality I guess.
My fav is AB2, extremely polished and claustrophobic. At a time when the italian version of 'The Games Machine' mag had come to reviewing 1-2 Amiga games max and 20+ Pc ones, leaving no mention to Amiga games whatsoever in the cover for months, even years perhaps, AB2 made it possible, ("the Amiga amazes still", they shouted in the cover), complete with full review, work in progress and Team 17 interview.
Tower Assault was good, with milestone CD32 intro, but the first level was horrible. (ducking bombs and canon shots?
Don't know about 3D versions, hated the idea 'cause 3D was Pc territory. Played AB3D only for 1-2 minutes or so, many years ago and still remember the great atmosphere and playability.