But im not good in flash, so i forget about that.
Flash isn't all that hard. You just need the Flex SDK to compile your games. You don't need any other Adobe products like CS Suite to build Flash games. Having Flex Builder does make developing Flash apps easier though and it's not free.
From a user's perspective, a native HTML 5 solution is a win, but it needs more time for adoption and bug fixing. I would still put favour on Silverlight for development right now. You also have out-of-browser installation, so people can play from their desktop. Unfortunately, you're looking to do multiplayer and that's a tough problem to solve with any of the technologies. Neither web sockets, Silverlight, or Flash will allow you to host a game server on the client, so you're going to have to relay messages from a dedicated server. It's pretty tricky to setup and do right, so you may want to hold off on that till last.
what do a RTS need for you to like it and play it again and again?
I don't know.. strategy maybe? :lol:
How i can make it free but still get some money with it?
Ads or donations. Ads require quite a bit of effort to setup (tax laws and stuff), but generally have a better payout. Donations are easy to setup, just setup a paypal account and away you go, but the payout is usually not that good (unless you have a lot of gratuitous players)
As for publishing, host on your own server for sure. If for whatever reason other sites don't support your technology, convince them or at least setup an affiliate with them.