Since Super R-Type is pretty much R-Type II you can get a proper arcade port of it on XBLA in the R-Type Dimensions package.
I used to think that Super R-Type was just a port of R-Type II with an extra level tacked on the front, but having played R-Type II a couple of years ago there are further differences. For instance, the water levels have completely different bosses in each game, and the typical R-Type giant battleship stage involves multiple smaller battleships in the arcade game, while on SNES it's one giant ship more like the one in the original game. I still prefer R-Type III over both versions.
I'll probably be laughed out of the forums for this, but my top 20 definitely would have included Super Ghouls N Ghosts...
I'm a big fan of Super Ghouls'n Ghosts of course, which is why the closing music for this episode was taken from the game's credit sequence--I thought it would be a nice choice because apparently a lot of people wouldn't have heard that particular song before!
BTW, the 0.9 multiplier for pound prices isn't based on the dollar but the Euro. The pound prices match the Euro prices, that's why DSi points cost more than Wii points.
Obviously the UK prices are directly derived from the Euro prices since all of Europe shares the same eShop. However, the nominal prices on the European eShop are generally 1:1 with the prices listed in North America, so the 0.9 rate still applies from USD to GBP. And when I, a British person, am discussing eShop pricing with my three colleagues in the United States, the natural tendency is to speak in terms of pounds and dollars rather than the euro.
And yes, DSi points/eShop credit cost more in pounds because those price structures were implemented after the financial crisis caused the pound to lose a significant chunk of its value against the Euro--when the Wii launched in Dec 06 the pound was worth 1.5 euro, by 2009 that figure was down to about 1.1.