Since you said "mildly experienced" (and also because of the fact that you actually have to ask), I recommend you use C#.

Though I'm a C++ fan and a real C# hater, C# is probably the best option for you. A mildly experienced C++ programmer is outright harmful. C++ is a nightmare if you don't know exactly what you're doing. If you want to use C++, you should be absolutely certain about it.

A mildly experienced C# programmer is mostly OK. It's much harder to completely fuck up using C# and you have a much more complete standard library (and a standard library that doesn't quite so easily lend to errors). So, all in all, you're much more likely to get a working game up and running if you use C#.

As for XNA, I wouldn't choose something of which I already know it's not going to be continued before I even start. While this doesn't automatically mean that XNA is "dead", it sure isn't a perfect going-in position. Even if MS currently says that they're going to support it (for... unknown time), it's some uncertainity. They might change opinion next year or with Windows 9 or with Windows 10, you don't know. Making a game can take years, so having something that has a somewhat "indefinite future" from the beginning isn't the best thing. Not when there's a good alternative, anyway.

For games, any languages that supports a graphics library will be enough to start writing games.

and user input, otherwise it is just a movie.

right! how could I have forgotten that...! nice save =]

I'm using RPG Maker at the moment. Well, I'm trying it out at least. To each his own.

I used rpg maker xp before I got into programming. I would say it is an awesome tool for designers: testing animation and prototyping area design and gameplay. Importing custom made scripts, sounds and adding sprite sheets into rpg maker is easy and the results are quick.

Adding triggers for events to happen in game is fun and I think it does help somewhat in understanding how game logic would work in a small degree.