RAIDEN LEGACY / DotEmu / Android
Raiden Legacy was my second arcade-action game ever on a tablet ... and like the first one (Metal Slug 3) I found it to be a perfectly fine port (well, collection of ports) ruined by the fact that touch control just sucks for games that aren't originally designed around it.
If you're not familiar with the Raiden games, they're Seibu Kaihatsu's series of 194X
clones, but instead of being set during WWII, they take place in space in the future, and everything just has a sort of vaguely WWII-ish look to it. They're very solid shooters altogether, and this package includes the first four - Raiden, Raiden Fighters, Raiden 2, and Raiden Fighters Jet (Raiden III and IV presumably being saved to be pimped in some future collection.) As with Metal Slug 3, they seem to be very good ports, look good, no technical issues.
The problem is entirely in the default touch control. First, you're flipped into "cocktail mode" automatically (you have to hold the tablet vertically); nice for larger playfield and more arcade authenticity, but it also eliminates using a docked keyboard as a control possibility. You simply guide the fighter around the screen with your finger; it's constantly firing its load at maximum rate, there's no fire button. Translucent buttons for the bombs and missiles are in the lower right, and usually aren't in the way, but can potentially be when things get really frantic. A bigger problem is simply that no matter where you position your hand, it's going to be blocking some segment of the playfield, and with all the tiny pixel bullets flying around you're often obscuring one that's coming right at you. The controls also feel slightly laggy and not as 100% responsive as playing with a pad or stick would be.
If you CAN hook up a pad or stick (and I'm not even sure that's a possibility with this game), it's a nice well-emulated package and probably worth the low price it's going for ... but you've also killed the portable aspect, and if you're playing it at home, you probably have a "real" computer or console that would be better suited for playing it on instead. There's nothing really wrong with it other than the touch control, but touch control is such a problem that I can't really recommend it.