If you're
really looking to make games for the web, for the love of god please don't use flash.
I realize a lot of popular sites like Newgrounds, Armor Games, Kongregate and the likes all use flash, but as AlsoSulfate said, it's dying, and it's seriously inferior compared to the speed and capabilities that HTML5 can provide alone, with or without <canvas>.
Unity is a popular option, there's also the option of using JavaScript/HTML/CSS to create your game, using a framework such as
Crafty.