You can pretend that you can make any kind of game, but there are only 24 hours in a day and you're only one person. Some kinds of games are only possible with a group, not by yourself. Simply based on the time requirements. Online games require customer support and community management staff. Online games also require information security and system administration staff. They also require professional artists and marketing and web development and all that jazz. You are only one person.
If you want to make an indie MMO, it'll look and play like trash and nobody will play it. Because when you spread your time so thinly, you can't be great at any particular aspect of it.
Here's an indie MMO, and it sucks ass and nobody plays it:
http://www.planeshift.it/And despite it being complete ass, it still took them a ton of time to make.
If you want a good game that you can make by yourself, don't make it online, don't make it 3D. Even if you can use a 3D game engine, you're either going to use stock 3D assets or just make really ugly 3D models. It's easier to make good 2D art.
2D single player is much more doable for indie devs who are working alone. You really can't argue with that point, but you will anyway for some reason.