None of them. The "Worf Effect" isn't about bringing a character from another series. It is about bringing in a character that is interesting, and "Rounding out the ensemble". This doesn't mean the existing cast wasn't good, just that something was missing. Worf did that for DS9, Seven did that for Voyager. DS9 and Voyager had a serious cast holes. TOS had Spock, TNG had Data. DS9 and Voyager had no such standouts, or the characters they were expecting to be standouts just didn't work as well as expected. I remember Kes was supposed to be this character for Voyager, but they just had so much trouble writing for her. Anyway Seven was the Worf of Voyager.
I am going to go with Q. Do the fallen God thing beyond a single episode. Limit his powers to being smart,shapeshifting and limited range teleportion and even those can go all wonky and not always work. Jayson
Umm... have you actually seen DS9? They had layers upon layers of interesting characters in the main cast and the side characters. I hate to say it, but Worf brought little-to-nothing to "round out the ensemble." It was intended to bring in more TNG fans who were still uncertain about DS9. As for your comment about Seven and VOY, Kate Mulgrew made it quite clear what everyone knew at the time, that Jeri was being brought in for her looks - which created a rift between her and Jeri since it meant axing Jennifer, and it seemed to work against Kate's own vision of building a strong female character without using sex appeal (which Kate has spoken on) in her own role as captain. "Rounding out the ensemble" had nothing to do with it. Saying that "TOS had Spock, TNG had Data," did you forget about poor Tuvok? He was that Vulcan on the VOY bridge all the time.
I have watched DS9 over and over. You have a right to your opinion, but everything I have ever read about DS9 say the show didn't have much focus before they revamped and brought on Worf, and I agree completely. I know all about the "rift" between the actors, on Voyager, and I don't care. My opinion is that like Worf for DS9, Seven was the most interesting thing to happen to Voyager. I think the "sex appeal" was irrelevant, it was a standout character. It added a Spock/Data like character that was missing, It just so happened she also had boobs. Jeri Ryan was excellent in the part, and that's all that matter to me. I did not care for Kes because I thought the character was limited and uninteresting, and I didn't like the actresses performance. "Warlord" is on my least favorite list. The writers had a hard time writing for her (but changed their minds once they got her canned) The idea that Jeri Ryan just came on the series and flashed boobs for ratings is ludicrous. The acting and story lines the character brought to the show were top notch.
Who Is pretending Tuvok wasn't on the show? Tuvok happens to be my favorite Voyager character, and I loved how Tim Russ portrayed him. I wish he had a few more prominent episodes. My favorite Tuvok line: Tom Paris : Ah! I give up! Chakotay : After only two minutes? Tuvok, how do you do it? Tuvok : I wait until his own illogic overwhelms him. But he wasn't the character who was trying to grow beyond his internal conflict. Spock was half human, struggling to become less human, Data was a machine struggling to become more human, Seven was a former drone struggling to regain her individuality. Even Worf brought that internal conflict (a Klingon living amongst humans) to DS9. These type of characters are easier to write for, and can generate interesting story lines. That's why Seven was added.
Yes, I cited that line myself in another thread. Tuvok repeatedly shared Spock's perplexity over humanity. Captain Janeway / Kate Mulgrew would disagree with you vehemently.
She might... but I get to be objective, and she doesn't. I like Kate, and Janeway is my third favorite character, and my favorite ST captain. But that show needed Seven whether she would admit it or not.
When VOY was already relegating allegedly-main characters to the sidelines, it's hard for me to justify bringing in a TNG character when the likely result will be to push the existing characters even further out of focus. Picard could be interesting in the sense of tension between him and Janeway, but I can't see him playing first officer working out well for anyone. Though him finding Chakotay's balls could be nice. Riker would just make Chakotay look even more like Janeway's ineffectual XO by comparison. If you have Data, do you even need Kim anymore? Though him and Seven could have interesting counterpoints. Worf makes Tuvok somewhat obsolete. I can't see Geordi and Torres working together (well), but a two-parter where they came to respect each other could be kinda interesting. I liked the Torres-Kim interactions early in VOY and regret that they trailed off. Given The Doctor may be my favorite character of the series, bringing in Crusher would be...undesirable. I did like the Troi-focused episodes, but lord knows VOY could have used a counselor...I guess she's the best option?
Tuvok would would wipe the floor with Worf. His dad-trying-karate style is no match for the Vulcan master.
How about Troi, trying psychological warfare on the Borg Queen? ("Really, your majesty, such a ruthless quest for perfection usually is indicative of underlying feelings of insecurity".) Or Data with the Kazon (McCulluh to Janeway: "that pedantic little android of yours is even more annoying than you!" ) Seriously though, I think Data would have been the most useful addition to the Voyager crew.
You'd be hard pressed to find a character more useful than Data. Seriously. His abilities are awesome.
No argument that Data would have been useful to Voyager the ship, but I suspect he would have done no favors to VOY, the series, with regards to the existing cast. Though Data instead of Kim....
To improve the stories, I can't think of no one better than Garak. Plus imagine him in the middle of an army of hostile Maquis people!
Sure, not saying that Data's presence would have been good from a storytelling perspective -especially since we already had the EMH and 7. But yes, to the crew (i.e. from an in-universe perspective) he would have been most useful.
Storywise "usefulness to the crew" is way down my list of reasons to add a character. They're gonna wander for seven years no matter how useful their characters are.