Just like Chrono Cross, Valis X, Zelda cdi. It never happened.

Metroid.
Final Fantasy.

Definitely the Earthbound/Mother series ; ; heck, I'd wait 10 years between each one if I had to if they were as good as Earthbound (Mother 2).

Mother 3 was pretty good, I'm almost positive that if I actually understood more of the text it'd be a great game. ^^; but yeah, I wish they'd keep making more, although I think it's been confirmed that there's not gonna be a Mother 4. bah.

1. Sonic- 3D was not good to him. The Sonic Adventure games were decent. The others should never be mentioned again.
2. Crash- sucked after the first three.
3. Spyro- see Crash.
4. Final Fantasy- while the games are still good, the series is starting to crap out. VII, though still enjoyable, was where the decline started. The stories got worse, the characters less sympathetic, and it became super easy.
5. Donkey Kong- hasn't had a good game since Donkey Kong 64.
6. Megaman- atrocious after the X series on the SNES ended.
7. Pokemon- it feels like the same game over and over again. Why would I buy it again if I can play the version of 10 years ago for free, especially since the game was better then.

Not a single person has mentioned the game that immediately came to mind when I saw this topic. I think that's a sign of how drastically the franchise has fallen over the years. How about:

Mortal Kombat

Remember how huge these games were in the early 90s? They were essentially the Grand Theft Auto of the period. Nintendo and Sega fought a bitter, bitter war over who would get the rights to the home console version of the game. (Midway eventually put MK on both platforms.) It was such a big deal, the US Congress even got involved and held hearings on whether the game was too violent for children. The furor is the main reason why we have the ESRB rating system today.

Combining the Genesis and SNES sales for Mortal Kombat 1 and 2, the home sales for the two games reached almost 10m copies, in a period where hardly anything topped 2m. This was THE series that all the kids wanted to have. (I think a lot of our posters are too young to remember this period.) And now the franchise is completely dead, the latest version barely cracking 100k worldwide on the Wii. Because the series fell so enormously far, I'd have to pick Mortal Kombat as the most destructive fall. Even the crappy Crash, Spyro, Sonic, and Megaman games still sell several hundred thousand copies...

Hah.  That picture is epic.

Good pick.  I remember waiting in line to play Mortal Kombat 2 at the store against others.  It was the unspoken rule of the display game that whoever lost went to the back of the line and whoever won kept playing.  My Shang Tsung and I played quite a while.  ^_^

Breath of Fire:

The first two were meh, the third was awesome, fourth not so much.

Xenogears/Xenosaga

Xenogears awesome, Xenosaga (1-3) not so much

Soul Edge/Calibur

Soul Calibur 2 was the crest, its been downhill since
.

Killed by subsequent games?

Final Fantasy - It used to be about great story, characters, development.

Now it's about showing off graphics in cutscenes, lame characters and horrible storytelling.

Chrono Cross hurt chrono trigger... not sure if it's enough though.

 Civ 4 is still fun... but I think it's headed that way.

 As I understand it, the Earthbound series consists of three very well made. Just because they're not making anymore doesn't mean the franchise is destroyed. It's not like it got destroyed from a bunch of crappy sequels, more like it ended gracefully. (and on a high note I've heard, shame I haven't played any of the games)