I think determining whether a game is successful or not is really a subjective matter.
It depends a great deal on your objective as a game producer.
What is your goal?
Are you looking to maximize revenue or are you trying to showcase your team’s skill?
If you go for a simpler game, something revolving around mindless fun, it will appeal to a broad audience of players as it has a small learning curve and few barriers-to-entry. If you go for a more complex, detailed game, you have a better opportunity to showcase your skill in your work.
It’s important to keep in mind the demographics of Roblox’s player-base. There are a lot of younger people on Roblox. Depending on the type of game you make, you’ll have a different target audience. Younger people, especially preteens have a more difficult time enjoying games with steep learning curves and complex systems. Playing Roblox games can be considered a stress-reliever for many people. It’s what they play when they want to get away from real life responsibilities.
Games that are fast-paced or easy to pickup and play, often bring enjoyment quicker. Think instant-enjoyment vs. enjoyment over time. People can be quite impatient, so games that bring that enjoyment early-on tend to be more popular, hence the list of games you see on the front-page. Games like the ones you mentioned are very friendly to the user. Meep, Welcome to Blox, Royale High, Jailbreak, those are all games that are fairly easy to pickup and understand. This is in comparison to games such as Phantom Forces which may require previous shooter experience and a better understanding of combat systems.
There’s a concept called Average Visit Time (AVT). If people find your game frustrating to learn, it drives AVT down as players quit rather than dedicate their time to master the system. Raising AVT is about ensuring people understand how to play and enjoy playing. Games with high replay-value, or incentives to spend more time playing, have stronger player-retention. The more complex and more detailed your game is, the harder it is for the average Robloxian to learn. However, with complexity and detail, you have more room to showcase the talents of you and your associates.
So we return to the question, what is your goal?
Is your goal to take advantage of simplicity and to create a game that’s easy to understand and play?
If that’s the case, you can capitalize on the larger player-base to create a game with high player-traffic and large sums of revenue.
Is your goal to create an impressive display of elite developer skills?
You and your team can shoot for a masterpiece to impress your peers and fellow developers.
You have the freedom to decide what your goal is with your game, and that will dictate what your audience is when you present your game to the public.