Sandbox. Theme park. Skill-based. Levelless. "MMORTS." Free-2-play. Hybrid. Open world. 32,000 rooms! Classless.
Declaring what type of game you're creating can be good if it gives direction. However, it can also blind you to good ideas that aren't typical in your chosen genre.
Free2play is a good example. There's a hundred different ways to model a game that costs nothing to play. The obvious one is to sell equipment, mounts, pets... further on, intangible perks ("extras"): bigger bags, a wardrobe for outfits, dye to color gear, non-combat items... and finally, just sell the game in fragments. Newbie zones are free, and every zone past there costs a payment.
Sounds good, especially considering that every content patch you release nets you a solid figure of cash. You can easily measure how much a particular part of the game is making you to figure out which parts of the game you should capitalize on. If lowbies aren't paying for bigger bags, maybe it's time to increase trash drops from the mobs they're killing, or reduce the size of all available bags to make yours look more appealing by comparison.
Of course there's a wild other option for making your game free to play: Don't sell virtual items - sell physical items.
I'm imagining a digimon style game where the cards you get in real life have unique codes that you can enter in game to suit up your virtual persona. Then, using the computer client, battle people online just like you would battle your friends in real life using the physical cards. This way, the game costs nothing to download and to start moving around in the world, but players have to buy the cards to pimp out their characters. Alternatively, you could only offer vanity items via the cards, and have the rest of the online world run like a normal MMORPG.
Of course when most people hear "F2P" they don't typically think of a physical card game supporting a virtual fantasy rpg. That's the point: Just because your game shares a label with another game, doesn't mean you have to jump in their grave.
Also note that I don't advocate selling a physical product to support your software. I think it's a bad idea, but was a good example.