Um, we don't have a large group of people, especially compared to their other franchises. Google "Unreal Forum". The first result has 34,599 members, 8,851 of whom are active. The JCF has 3,545 members, with 308 active. Assuming the amount of forum members is proportional to how many people liked a game (which isn't true, but a true ratio would only sway it in Unreal's favor more), that means the number of people that currently like Unreal is more than twice as large as the number of people that ever liked Jazz, ever, and Unreal has at least 30 times as many fans.

A company doesn't make a game for 300 people. Off that group alone, they might make 10,000 dollars. That's 10,000 dollars to pay all the game's producers (animators, coders, etc) for however long it takes to make the game. For comparison, the guy that dresses up as Ronald McDonald makes 50,000 dollars a year. Assuming it takes only a year to make the game, and if there was only two people making the game, they would both be paid one tenth the salary of a man who dresses as a clown for a living.

Cooba is right; most important here is gameplay concepts. Making a good game isn't just a matter of making another Mario-64-ripoff platformer with different characters; it needs an original premise. If you want to be helpful, you're better off focusing on gameplay rather than story.