Not very simultaneous
The "simultaneous" availability of games has nothing to do with the developer/publisher per se - in fact its the holy grail of all mobile games developers.
The reason games don't get launched simultaneously is because the Networks have backlogs of 3 - 6 months on their QA decks and have different cycle times for picking up the content. So e.g. you might submit a game simultaneously to Orange, O2, Voda, 3, T-mobile, yet the response time for acceptance of the content can be anything from 1 week to 3 months (or more). Don't even talk about getting the operators to launch them simultaneously across Europe.
The simple reason mobile gaming hasn't expanded is because the Network operators make it too difficult and too expensive for the punters and too difficult and too expensive for the developers.
Here's a little classic - PAYG customers on O2 still can't access WAP => WAP push by default. When over 75% of your customers are on PAYG plans, how on earth do you expect to expand your content market ?