Which of the five to open first
They have almost nothing in common beyond the look, so the useful question is what you are in the mood for rather than which is best. Neon Breaker is the most familiar - a bat, a ball and a wall of bricks - and it is also the most configurable, with a sandbox mode that lets you change the rules while you play. If you want somewhere to start without learning anything new, start there.
Neon Rise and Neon Void are both endless climbs with no finish. Rise is the gentler one: you bounce automatically whenever you land, so all you ever do is steer in mid-air. Void is the hardest thing in the collection by a distance - you grapple onto orbs and swing, and the boost only counts if you let go while you are still travelling upward.
Neon Core and Neon Catch are the two short ones. Core is a defence game played around a centre point, and Catch is a pure reflex test. Both are the sort of thing you play in a spare two minutes rather than settle into.