So this is completely obvious. But I'm going to say it anyway.
Generally speaking, D&D is the hobby. It is damned easy to find players. Also, in my experience, it is damned easy to find good players (by which I mean, people who are fun to game with). There are a lot of people to choose from, so a lot of them are fun to game with. It's the numbers.
I run an open table, and I use an email list with about a dozen names on it to announce weekly games. For about eight months last year, I ran a Mage: The Ascension game as the main campaign. One time we had eight players (I'm not counting myself in these counts). A number of times, we had five to six. Fairly often, we had four. But most weeks we had three players. Over the last few months of that campaign, we were consistently seeing the same three players making it to each session. They were the Mage audience.
Once Mage wrapped up, I pitched D&D. The email list lit up. Last week, we had eight. This week, having announced the game mere minutes ago, I'm already seeing the confirmation emails pouring in. I expect a good-sized group again.
One more thing to love about D&D.