B.Collins, it's not a stupid question. At the same time, you have to take all the info that you get from IMDb, blogs, entertainment websites, etc. with a grain of salt. Not all of the projects are real- many are just silly rumors, such as Johnny being The Riddler in the next Batman movie, which *still* keeps popping up. Even when an upcoming project is real or at least a real possibility, you have to take into account that many are years in the future, so realize that his agent is thinking of his longterm career and wants him to have staying power. Also, the agent would still be thinking of possibilities in case something falls through, as so often happens in Hollywood. Johnny hasn't necessarily "signed on" for most of these possibilities, and the same is probably true of Will Smith, though I'm less familiar with Smith's career. Finally, at least on Johnny's list, many of the titles listed on IMDb as "in development" are ones that his production company is developing, that he may serve as a producer on but won't star in. His career as a producer is just beginning, and many of the titles that his production company has options to produce are just possibilities- some of them may never even get developed. The same may be true of Smith, too- I don't really know if he does any producing.
As far as Johnny's titles on IMDb:
The Thin Man- sounds like he will produce and star, but this is years into the future- there isn't even a screenplay
Wild Roses, Tender Roses- this one is probable. He is a friend of the producer, Emir Kusterica, and was originally slated to film this in early 2011, but it was pushed back a year or so, in part to make DS filming possible
My American Lover- Johnny and his real life love, Vanessa Paradis, want to star in this, but it is probably a couple of years off. I don't think there is a screenplay yet
Caliber- it has been said that Johnny would only produce, not star in this one
Affected Provincial's Companion- ditto
Inamorata- ditto
Dark Shadows- well, hopefully it will film in April!
Rex Mundi- I do think he wants to star in this one, but it's been in development for years, and I haven't heard any news on it in awhile. It's probably still a few years off
The People's Act of Love- I think he'd produce but not star
The Lone Ranger- he would star in this, and it may come up fairly soon, as I think there has just been another screenwriter hired (similar to what happened with DS)
The 83rd Annual Academy Awards- huh? I don't know why this is on there
In the Hand of Dante- I think he would only produce, not star
Happy Days- ditto
Shantaram- yikes, he wanted to produce and star in this one, and it almost got started 2 or 3 times, but it is in turnaround now. I don't know if this film will ever get made at this point, and if it does, Johnny may no longer be attached
Sleeping Dogs- this is the Kathryn Bigelow film that seems unlikely now that Johnny has a specific start for DS, but it doesn't seem to have been officially ruled out yet
To add to IMDb's list, Johnny is still planning to produce (and probably appear in) a Keith Richards documentary, which filmed in part early this year. I don't know what the status is of that.
Hope this helps, and hope it wasn't too much boring info. Just wanted to convey that such a long list isn't really that long when taken item by item.
Edited to add-- wow, I just realized that IMDb has finally taken off that stupid Incredible Mr. Limpet rumor, which I have never seen or heard credible evidence for. Thank goodness!