Anyone want to do something useful and rank those games best to worst?
Or just compile a top 3/5/10/20?
Not a top, since I didn't use any qualitative order, but here's a few of my picks from the Steam sale that are worth a look, IMO:
DARIUSBURST Chronicle Saviours
Crimzon Clover WORLD IGNITION
Raiden IV: OverKill
Triangle Service Shmups Collection
DARIUSBURST Chronicle Saviours is my clear favorite. It already became one of my favorite shmups. It may be more expensive than the other titles, but it has plenty of content, modes, and plenty of references to past titles in the series (from old ships, old soundtracks, ...). IMO, it's a blast to play.
Crimzon Clover WORLD IGNITION, Astebreed and REVOLVER360 RE:ACTOR are usually cheap, and very fun titles. You can do no wrong with any of the three, which are all very different from one another.
Deathsmiles and Mushihimesama are Cave titles, with many available modes, some imperfections in the ports, but very worthwhile nonetheless.
The Triangle Service Shmups Collection has plenty of titles, and are an enjoyable diversion (the individual titles are also for sale).
Sine Mora is disliked by some people (either because the stages are too long, or because enemies take too many shots to die), but I find it quite enjoyable, it looks lovely, it has a great soundtrack, and some interesting enemy designs. And it's quite cheap as well.
Renegade Ops is a bit unlike the other titles (it's more of a stage-based, free-roaming game where you control either land or air based vehicles (it depends on the stage), and blow shit up; the story is pure 80's Saturday morning cartoons), but it's a very fun title, and again, it's being sold for quite cheap.
Waves and Scoregasm are score-based titles similar to, say, Geometry Wars. If you like the genre, both are worthwhile.
Raiden IV: OverKill is a more traditional shmup, but it's still very enjoyable, and worth a look.