Hello my friend.
To be honest, most of my games are made with GameMaker, GameMaker is
awesome game creation tool, and of course Construct 2 is the best too
so far in the HTML5 field, both engines have their pros and cons in
different angels.
For the Pros of GameMaker 8:
1- Got GML (scripting)
2- Room Editor
3- Support Tilesets
4- Support Sprite Sheet (PNG)
5- You can Extend it (DLL/GEX)
but for GameMaker Cons:
1- Despite the support of Drag-Drop you still need to learn GML, which
may not friendly for non-programer users for good functions.
2- Screen Tearing Issue.
3- Can't resize or rotate sprites and object images inside the room
editor
4- for HTML5 version, don't support WebGL (Yet)
For Construct 2, the Pros Goes:
1- flexible without programing for most part of features.
2- the game programing via events style, which is very organized and
fun to create.
3- Can rotate and resize object sprites inside the Editor, like send
object to front or back.
4- Support Behaviors, like platform which can easily applied.
5- Fast Fixes and Frequent Updates (Thanks to Scirra) for bug fixes and
new features.
6- Support WebGL for HTML5 (fast performance)
But for the Construct 2 Cons, we have:
1- Can't Support Scripting within IDE, (although indirect you can
use the C2 SDK).
2- No Tilesets supported (Yet).
3- Can't copy Layout (Yet)
That's all so far, but one thing made C2 so unique is, you can import
GM HTML5 sprites and tilset to the layout !!
scirra.com/tutorials/63/importing-gamemaker-rooms-and-objects-to-construct-2-free-edition
it's like, C2 is your second wife that don't mind to befriend with your
first or ex-wife(GameMaker) XD (just a crazy example)
the Both engines in my opinions are great, and if you can get them both
i see no problem with it, but if you deciding which one suitable, just
give them both a try and good luck <img src="smileys/smiley2.gif" border="0" align="middle" />
Regards~