I'm surprised Haxe + OpenFL hasn't been mentioned either Michoko. Not to mention, there's a fully fledged and maintained Starling port in Haxe now too.
I've been doing the odd bit of developing with Haxe + OpenFL for years now, but the bulk of my work was/is still in AS3 + AIR. It's fair to say I've used it as often as is feasible. Most of my projects over the years have incorporated video and/or webcam, which is why the tendency has been for AS3 + AIR, which is definitely stronger in that respect.
My current active project, a gamefied training app, is Haxe + OpenFL + Starling.
It's really quite an easy transition. I use the same tools to develop (FlashDevelop, TexturePacker) and it has a near identical syntax, albeit stricter in Haxe. It's the closest thing we're likely to get to a spiritual ActionScript 4.0.
You've got the ActionScript 3.0-like language in Haxe, the Flash-like framework in OpenFL and the literal port of Starling in... well Starling.
I have no strong desire to gravitate towards another proprietary system, such as Unity. If not Haxe/OpenFL, I'd likely look elsewhere first. Godot perhaps, MonoGame, WaveEngine, to name a few. I've used OpenFrameworks and Node.js for some projects too.