WHAT KIND OF STORYLINE DO YOU PREFER?

My beliefs are that those are both extremely basic, very represented concepts that are so vague I couldn't really choose one or the other without further context. I also believe you shouldn't put your game's features and design tenets up for vote, you should develop a clear image of your goal and pursue it.

author=DungeonMastersInc
(A) would be the generic storyline everyone loves

Please never use 'everyone loves' 'generic storyline' in a sentence ever again.

(B) is more of an interactive story (has less game, but is still role-playing) and the plot doesn't revolve around just a few people, but about everyone on the planet.

de facto preference would then become option B

Sorry mate, but you’re not going to get a unanimous vote. Both projects will have a target audience, and you should be thinking about yourself, not us. If you’re equally in love with both of your stories, that’s really great, but I think you should start on whichever project that might have less of a strain on you, so perhaps the project with the smaller cast? A single project is more work that you might realise and my gut tells me you’re a beginner, not to be rude.

I think it's extremely difficult for the player to get attached to a story without characters. SaGa Frontier 2 is an interesting example of one way to do this. It's non-linear, and you start out with two main characters, but each of their dungeons is set several years after the previous one, often with a partially or completely new supporting party for them. Then as the game goes on you start following some of those supporting characters as well, and then start following characters that they meet, and so forth even after one of the original main characters is dead and the other is eighty or ninety years old. It tells the story of the world, and even though the two main characters are of major significance in the world's events, the game doesn't treat them with any special significance. Characters aren't developed beyond the minimum needed for the events to make sense.

However, in SaGa Frontier 2, as in other games I've played that don't really have major characters, I find it hard to care about the story. Controlling one or two single characters with real personalities makes me feel connected to the actions of those characters. In a game like Chrono Trigger, which is very much a story about the world, I feel connected to the world because my party - my avatars - were involved in shaping it, and because I've gotten attached to those characters to the extent where I feel like they represent myself. If I do not have an avatar in the game, then during cut scenes I feel like I'm watching a movie. Like it's not my story. This is the reason why backstory and lore is less exciting than events the player is involved in - it's not simply because the player wants to push buttons to make things happen (although that's part of it), it's also because the player wants to feel more connected and involved on a personal level.

All this said, if you only have a small handful major characters that the player's viewpoint switches between, I think it works fine. Final Fantasy 6, Suikoden 3, Warcraft 3, etc. all successfully switch around the player's viewpoint multiple times without affecting the player's ability to empathize and connect with the characters. The key here is that the characters you play as are still well-developed major characters with depth and realistic struggles - there are just more than one of them. This is easier to do in a longer game, because you have more time to let the player get attached to each character.

I think I need to care about the characters in order to care about what they're doing and what befalls them. If one person dies it's a tragedy; if a thousand people die it's a statistic.

I was going to make a blat about how the only thing that really mattered was making a game fun to play. However, this:

Rather than trying to cater to a demographic, you should just work on the scenario you think you can make the most of.

author=DungeonMastersInc
B) a storyline that tells a story that spans many characters (no "main protagonist(s)").

You mean kinda of like Dynasty Warriors? (in which there are 4 different kingdoms that all combat one another in order to unite the land, and you can play as all 4 in whichever order you want). Obviously, that's not a GREAT example, but it's what came to mind first.

If it's anything like Dynasty Warriors, though, I would say go for that one because I love Dynasty Warriors it could potentially be more interesting.

Actually, both games would be interesting. It doesn't really matter which you do first. So, just for no reason, I say go with game "B."