
First what makes the Combiners so popular with fans? Because its group of transforming toys that combines together. It's also a good way to make money. I personally prefer 5-6 team members with the same height better which are also the mean characters. The newer toy lines seem not to have any of them other then the RID and Energon lines.

Second, what make Power Rangers so popular? because it has combining toys that combines into one big robot but Transfomers can do better with transforming action figures which are also the combining toys too while Power Rangers action figures are rubber suited duds that don’t do anything much.

Third, I personally prefer a TF toy line that looks like TF Victory or Takara's Brave series with a leader or an ultra class figure as the leader bot or con, each faction have two combiner teams with each figures as deluxe class so their Gestalt form would be leader class size.

Lastly, instead of using the more popular Combiner concept Hasbro decided to use super heroes style for the new cartoon and Hasbro think this art style is popular with kids today.