My son will be having his fourth birthday next month and I would like to invest in some good play value action figures. He wants to have Superman, Batman, Spiderman, Iron Man etc because the kids at school have all these heroes emblazoned on thier T-Shirts. Are there any toy lines currently that do a decent job of making figures for both DC & Marvel that are compatable with playsets and vehicles?

Hey Man Sorry I missed this post earlier.
My suggestion is get those 3 inch figures. They're compatable with gi joe. and alot of other lines in that scale. That way you could mix in the stuff.
But if you want playsets they have very tiny 3 and up playsets of spiderman and a villian at toys r us. they're about 10 dollars a pop and If I were 4 I'd play with them. Hope your kid has a blast.
If you need anything else just reply :D