These two franchises were early pioneers for their time when they made their debut on the SNES, but why has Nintendo stopped continuing these franchises? As a kid I loved F-Zero. It was really a one of a kind racing game when it was released. I wasn't that big on starfox until I got my hands on the reboot Starfox 64 which won me over with it's comic book storytelling and action sequences.
Over the years these two franchises lay dormant due to underwhelming sales of their games. There hasn't been a new F-Zero game since 2004 and Starfox hasn't released any new story elements since 2006. To make things worse, both have been largely ignored during the Wii era (aside from Smash Bros. Brawl). However Starfox is starting to show signs of revival after the N64 game was remastered for the 3DS in 2011.
Despite the underwhelming sales and mixed to positive reviews of these franchises acknowledged by Miyamoto, they do have a cult following and deserve better recognition. The question here is why weren't they doing well?
There could be many reasons. In my opinion, F-Zero's interest started to wane mainly due to players demanding more "realistic" looking racing racing games. Players these days preferred stuff like Need for Speed, Gran Turismo, Project Gotham and Grand Theft Auto(though technically not a racing game) just to name a few. There aren't many futuristic arcade style racing games out there, though I could be wrong. All I see from Nintendo these days when it comes to racing games is MarioKart.
As for StarFox, it may have gotten overshadowed by other aircraft simulation games. Maybe the Star Wars games played a factor. Maybe people just got tired of 3D railshooters. Or maybe some people got tired of the use of furry characters. I really don't know. Again, this is all opinion.
All I can say is that these Franchises need to be brought back somehow. They both still have a lot of untapped potiential that need heavy emphasis on introducing new ideas to make them feel fresh again.
Out of which, I have several good ideas for both franchises that can work for future games:
a) focus more on Non-linear routes (Ex: Starfox 64)
b) Co-op online multiplayer gameplay (optional)
c) customizable ships and characters
d) reduce or improve on-foot missions.
a) Expand James McCloud's story and keep his death a mystery
b) Make another spin off title with Falco that explains his absence during "Starfox Adventures"
c) continue the story with 4 of the 9 endings in command and branch them out as "what if" stories in the timeline.
Dash makes a choice,
The Anglar Emperor
a) customize vehicles with money won in races (ex: Star wars Episode I racer)
b) introduce weapons in gameplay (ex: marioKart or Extreme-G)
c) Make the tracks longer or add more laps.
d) Lower the learning curve for the casual audience.
e) Expand the use of customizable "roller coaster" tracks.
a) expand story mode and endings and include "true" rival characters for each racer (Ex: SF IV)
b) interconnect stories and characters (Ex: Resident evil 2)
c) If all else fails, reinvent the franchise and make it like a futuristic open world game like GTA.
One final suggestion. DO NOT MERGE THESE TWO FRANCHISES TOGETHER! I mean seriously, a Starfox reference in F-Zero X? An F-zero reference in Starfox Command? um...weird...
In closing, if Nintendo does decide to make more games for both franchises, I will gladly save up to buy a Wii U. I've done the same thing in the past with the Gamecube (before realizing that the Wii was backwards compatible at the time) and Twilight Princess. There needs to be a petition for these games and deserve to be introduced to a new audience.
People want more Falcon Punches and Barrel Rolls!