We will not discuss which one is the better game. We will discuss the different trends and which one you might want to follow as a content creator. It seems like Minecraft had its peak around 2013 in terms of popularity. Roblox is winning ground and as of 2019 Roblox has surpassed Minecraft and went over a staggering 100 million monthly users. Without discrediting Minecraft, this newer MMORPG (Roblox) seems to have everything the gamers want. These games are all in the block-based sandbox building an digging games niche. Whether it is searching for minerals building structures, there is a high amount of creativeness to it. This makes these two games excellent for an audience hungry for being creative.
For pay-per-install, you obviously want downloadable content. Roblox seems to have a 'modding', 'exploiting' climate. It is not being creative within the game rules, but also outside the general gaming rules. There are tons of Youtubers that show how to 'pwn' another person with some tweaks to the game. While Minecraft also has mods, it looks to be more of a creative kind e.g. skins, which might be less fun and less viral.
If you create a whole channel aroung gaming, you obviously don't need to stich to just one game. You do however want to be certain that it is not a dying game. If there is one thing you can be sure of, it would be that Roblox is not a dying game. There is tons of audience and place for you to claim your spot. There will always be 'crafting' games and it seems like a growing in popularity as well. Another point to make is that these kind of crafting and creation games are usually in the form of an MMORPG. This has a viral compontent to it. Since friends play together they are likely to share a video or wegpage with their friends. If you do hit the nail on the right spot, especially with videos, you will see this viral aspect. Without much efford some gamers just hit it right and gain a massive following in short periods of time. It is not a coïncidence that the biggest youtube has his roots in gaming videos on Youtube.
What makes these games so attractive? It might be the fact that there is so much freedom. You can literally create a game inside another game, which is pretty awesome.
Each gamer is forced to turn into a game designer when the goal is creating fun gaming stages. There are some built-in incentives and even gaming currency.
One final point. Games are usually bound to hype. The hype cycle might be a year, or even ten years. If the developer does not create more hype or innovate enough, there will be another game that will dethrone the old king. Which is maybe not a bad thing.