Cho Ren Sha is an excellent SHMUP, i'm no expert but it has to be one of the best i've played. every bit of design is something to appreciate, and the challenge of the game is very satisfying.

+apparently still actively being developed
+nice port of original.
+Really good music that complements playstyle and movements
+really fast and fluid action
+overal simplistic and mechanical play method free of gimmicks (except the power up system)
+really cool looking, parallax-y animated enemies with specific functional roles in this SHMUP ecosystem
+awesome bosses.
+excelent trainer. you will get better and this will make you better!
+hidden cheat menu for invincibility and more. (still challenging but at least lets you make progreess and can practice)
+Decent enough replayability
+Free

-limited keybind functionality, a lack of autofire will make your fingers tired
-background scenery doesnt change
-not the best sound effects, not bad, just dated. very much reminds me of 1942 and other arcade era games. (some may like)
-a solid test of memory, skill and ability to dodge becomes "bullet hell" in later stages.
-requires a NG+ (known as 'loop') to 'complete' game.
-name is impossible to remember