WHICH ENGINE SHOULD I USE.....?

I would suggest Game Maker. It has a lot of flexibility, it would be a lot more suited to platformers than RPG Maker. I have perceived that is also a lot more suited to 2D games than Unity, but some do advocate the 2D power of Unity. I just think for a relative beginner Game Maker would be easier to use.

Edit:
For example, Spelunky was made in Game Maker. Here's what it looks like.



It is also available for open source, if you wanted to check that out. I have done so, even if it's a bit messy. halibabica would definitely be the dude to ask about this game.

Stencyl is a free-to-use, flash-based game making tool that can make all sorts of 2D games: from platformers to shoot-'em-ups to rpg's to gta-clone, name it. It can also publish into many platforms, including iOs and Android, in case you'd want to reach those markets. There are also quite a lot of informational material and pre-built resources available in the net. Their forum's still quite active too.


And yes, I was Stencylin' before I was RM-in'. Just saying...