Currently all the major software manufacturers are working on their mobile slots portfolio's. It isn't a case of just resizing the original online games to suit a particular device. Many of the new slots are being built in html5 and have to work across a number of different devices, screen resolutions and operating systems - sounds like a nightmare to organise. Added to this is the fact that new devices are being launcehed all the time, eg iPad mini, Microsoft Surface etc etc...
Anyway, at the moment most of the big software providers Microgaming, Playtech, Net Ent, IGT have between 5 - 10 slots each and a selection of table games and video poker. Therefore, if you want more choice then you probably need to set up an account at somewhere like Mr Green, which has both Microgaming, IGT and Net Ent software. Alternatively you can sit tight and wait for the roll out of more games.