It sort of depends on your ambition level I think.
But you also need to put HTML into perspective. HTML is not hard. HTML is a couple of tags for headlines, text, hyperlinks and images thrown together to make those things appear nicely on a webpage.
*After* that people have been throwing together PHP, ASP, CSS, Java, JavaScript and many other things in order to make HTML do all sorts of stuff it was never meant to do in the first place.
So if you're thinking, "Boy, HTML&CSS&JavaScript&PHP&ASP&Java" looks hard, then you're absolutely right, because that things a mess.
HTML in itself though, that one's easy. Much simpler than Ren'Py.
Now, back to the ambition level:
If all you want is to have you and a friend connect to each other by ip-address or something like that, then probably you could do that with Python, which has extensive libraries for such a thing.
And then you could let in-game events be dependent and what you both did - player1 chooses 'fight', player2 chooses 'magic', and consequences unfold - and if such a game is fine, I think it should be doable.
On the other hand, if you want strangers to be able to connect, you'll need to write a server program.
If you plan on a lot of players, you'll need to write a good dispatcher to tell a bunch of servers to deal with the info. And plan on a strategy for dealing with overload and such.
Eve Online was written in a variant of Python,
Iron Python Stackless Python (thanks for the correction), which was optimized for dealing with something that enhanced responsiveness - something with thread support, I think.
There might be an game engine somewhere that'd let you write something like you want.. but aside from looking for one such, also try following a python tutorial for connecting two computers over a network.
Edit: Xela's approach sounds good too. That is one nice-looking tutorial for a web-based game.
Edit 2: Asceai is right, sorry.. Iron Python is Python for .Net, which is quite another thing.
