The paradox of UFO 50 is I find it equal parts compelling and frustrating, but if it were like, "UFO 5", and it had consisted entirely of Velgress, Kick Club, Hyper Contender, Magic Garden and Pilot Quest, it would be one of my favoritest game collections EVER.
(To gild the lily, maybe hide in Barbuta, Mooncat, Camoflage, Campanella 2 and Star Waspir as unlockables, becoming available when you beat the 5 main games.)