Well, there are many types of roleplays. If you want a sucessful one, you should make one that appeals to other people.
The two main categories of roleplays are:
Fanbased -using a roleplay based on/from a show, book, etc. Tamagotchi roleplays would go into here.
Storybased- using a story that is not pre-existing.
The benefit of having a fan roleplay is that you have a set audience. However, you also immediately exclude anyone who is not a fan of said series. The benefit of having a story based roleplay is that you are open to everyone, but they aren't as popular as fanbased most of the time.
Now, the people in a roleplay do sometimes matter, as who joins makes a roleplay more interesting. There are three types of roleplayers:
Illiterates: pyonchit: *waves* hi tdawg!
The content of one's posts also determins wether one is illiterate or not. Usually, they do not use proper grammar or sentence structure.
Literates: Pyonchit waved, and walked over to T_Dawg. "Hello!" she said with a smile.
Proper grammar, punctuation, etc. Usually the content has plot development and other.
Advanced: There is only one advanced TTer right now that I know of. If she joins, I think you'll know.
There are some subcategories, too It can be a combonation.
-highschool (college/ dorms included..)
-gifteds (nekos, powers, etc)
-dark (vampire, werewolf)
-IRL(in real life, which could mean things like orphanages, etc)
-Wolf/cat roleplays
There are more, but these are the general.
So, next time you make a roleplay, think about these things a little bit. I know that most people actually don't really think about these things, but I think you won't come down to advertising your roleplay in the forums.