I think this a very simple view. I agree with you that depending on the language the syntax will differ but it goes a lot further than that. Especially when you look at mobile app development. In Java (for Android dev) you don't really have to pay a lot of attention to memory management, but in Objective C++ you will be exposed to pointers and memory allocations. There are also fundamental differences in the way you develop UIs and how UI managers manage the UIs across the different platforms. Other aspects are simple aspects such as push notifications - each platform uses a different way of achieving that.
It is true, to learn a new development language is easy, it's the architecture you develop on is the complex/difficult part. I would pick a platform which scales commercially and my opinion is:
- iOS: Great development environment and lots of support. Can only be developed on OS X, but Xcode dev environment rocks - simulators and debugging tools are very easy. Coming from C/C++ and now on Java I found ObjectiveC and the way UI's are developed difficult. But then again, I was never good with GUIs ;-). iOS consumer base is great, the users are used to pay for stuff - so a good ecosystem for paid apps.
- Android: It's Java and the language is dead easy. The Android SDK and simulators suck in my opinion - even on a MacBook Pro with 16GB RAM and SSD it takes way to long for the simulator to load. Remote debugging is okay but the whole development process is not as polished as iOS. Android consumer base is "cheap" - everyone wants free apps and you need to work on a commercial model to capitalize afterwards.
- Win8/RT: Sorry Microsoft fans - I consider this mobile platform still dead. It might be cool and awesome, but it has way too little traction that anyone would use this as a primary platform to develop against. Considering how much money the mobile app development costs, I would only look at Win8/RT to scrape out the barrel. I also think Win-users are adverse to pay for things ;-)
- BB10: (I like all things Apple) but just recently switched over to a Z10 (mainly because I got a free one - lol) - the OS is polished and the platform is "fresh" - so lot's of opportunity in the "new land" of mobile. The bigger companies are holding back and the developers hitting a niche first will reap benefits. The platform is easy and the user base (corporate users) is willing to pay.
iOS/Android is certainly a must have skill. If you are an early adopter (and by the looks of it BBRY will make it) BB10 is a promising platform to develop on.