1. Darla Deering
I feel bad putting her first.... I'd feel bad if I didn't.
Probably the real number one, out of all the many replacement members, she's the one who "took" the most. I guess we also ought to discuss which member is the best to BE replaced. I wouldn't have thought it was Ben, but this worked.
3. Ms. Marvel
I don't feel that the Fantastic Four is the kind of comic where the subject of rape should really be featured, not even that time when Ben got pushed into a volcano in the Lee-Kirby run. Nevertheless, despite some questionable "not for the kids" content, she brought some drama to proceedings.
Could be higher. I always felt they were reaching too much with dialogue like "Medusa's invincible with her amazing power of moving ginger hair", but she worked okay within the team. I've got a lot of nostalgic love for the period, and she showed that her efforts with a vase made Ben's Sunday best look weak.
The opposite to her sister, in that you had someone so highly powered that she could conceivably take out the entire team, but they played it down. I was always surprised how little she was allowed to do in the Lee-Kirby run, and it was more Englehart where she came into her own.
6. Ant Man
Mainly for his run in that great spin-off title, which oozed goodness. Not so much for his run in the title proper, which wasn't much fun at all, and he seemed to think Johnny was after his underage daughter. Ick.
It says a lot for how much impact Spider-Man had that he was in the book and I completely forgot. It goes back somewhat to what I was saying earlier, about which team member gets replaced. Ben and Spidey has never really worked amazingly well (it's OKAY, but it's two wisecrackers together, they need a straight man) and Johnny was the one he always had the connection with. But Johnny was the one he replaced. Worse, Spidey was serious in the run, they were fighting in locations where his powers didn't really get used to good effect, and the team were mourning the death of Johnny so he was like an outsider. All in all, not a good fit... but he COULD have been.
7. Black Panther
AS with Spidey, then with some of these, it's not the character, it's how they're used. BP was a great ally of the group, but when he was a member it didn't really "click". And I still don't get how he can hold the Silver Surfer in an unbreakable headlock.
8. Luke Cage
I've got a lot of love for "Sweet Christmas!", though he didn't really do much when he was in the title.
She didn't really seem like a developed character to me, more just someone Bryne was exiting out of the book.
Anyone even remember Storm being in it? She had nothing to do, did she?
Below is my list. It may include a few characters who were not official replacement members but hung around the team long enough so they could be considered for "honorary" status.
1. Crystal: more for her first time around than her second. Her second stint didn't live up to its potential as Englehart became Harkness.
2. She-Hulk: probably the most effective all around
3. Ms. Marvel: I just loved her crazy
4. Thundra: I always liked the character and wish she had hung around longer in the FF title.
5. Medusa: Again, more for her first stint than her second on the FF title.
6. Tigra: like Thundra, I enjoyed her jumping around flirting with Ben.
7. Spider-man: always felt like a guest star and not a full-fledged FF alternate.
8. Nova: she was useful in developing Johnny's character
9. Ant-Man: I like Scott Lang. He shoved a tree branch down Doom's throat.
10. Darla Deering: Never warmed up to the character and her Thing ring
11. Luke Cage: He was really only in the title a short bit and at this time was a very one-dimensional character.
12. Black Panther: love the character, knew McDuffie could write him well but his presence on the team was stop gap.
13. Impossible Man: I think he's had enough appearances helping the team out to qualify as an honary member.
14. Namorita: easy to forget about because she didn't do much.
15. Kristoff: I recall him liking Lang's daughter. Did he get pissed at Doom when he killed her?
16. Storm: useless. I remember her just smiling a lot
17. Namor: I think he was a fill in member after Reed died. I hate him in the FF. He's always more enjoyable apart from the team.
18: Any Claremont created character like Caledonia or Bounty
19. Doom: Uncle Doom is last and least