Sausalito,
When I lived in Belgium, I always wondered about the.... no, just let me tell you that you are not the first to be surprised of this...

Oh my, did I say something wrong then?
I'm not a native English speaker.

Leonidas is by far the best. It is not a "category below" any of those mentioned. Your wife would love the creams - best chocolate and most flavorful creams I have ever tasted - the lemon is incredible. I must admit, I have never had Leonides with chewies and nuts - for that you may have to try Cote d'Or.

Leonidas is NOT "by far" the best. Nor is Godiva, Neuhaus, Corne Royal or any other brand. They are all high quality, but it's impossible for any one Belgian chocolate to be "the best" just as there is no *one* best wine or best perfume. It's all a matter of taste. Leonidas (or even Cote d'Or for that matter, a cheap, supermarket chocolate that I hate) can be *your* favorite, but it's still not really the best. As I said before, Sausalito needs to try a variety of chocolates, then buy what turns out to be his/her favorite. I've tried chocolate from more than a dozen high quality makers, but my favorite chocolate is actually the Schiesser brand from Switzerland...but that still doesn't make it the best.
FYI, if you like those Guylian shells, note that a portion goes to protect ocean environments (check www.projectseahorse.org)

BTilke,

Haha
I never go out of the way to taste some chocolate, am living since 20yrs in Switzerland, but I have never heared of Schiesser before. I just checked it out, it is a small scale chocolat maker in Basel. So I wouldn't say it is a 'brand'. You can find some other small scale chocolate makers in other towns such as Neuchatel, La Chaux-de-Fonds or Fribourg.
Maybe, certainly, their small-scale production guarantees their quality.

I agree with BTilke -- there's no single clear "best" among the hundreds of chocolate makers in Belgium.

I also agree with her about Cote d'Or -- when I first tasted it 20 years ago I liked it, but I don't now -- don't know if that's because my tastes have changed now that I've had more (much more) Belgian chocolate or because Cote d'Or changed after Kraft bought it.

I do like Leonidas -- it's a good, reliable, tasty widely available mainstream chocolate brand. But of the chains, I prefer Daskalides for a bit more money. At the higher end, I've enjoyed Wittamer. And there are countless others I've liked including Sweertvaegher in Brugge (years ago, I don't know if they still exist or where they are now) and a bunch of small places whose names I don't remember, especially a fabulous little place in Leuven where the owner, an ex-architect, handmade just about the best truffles I've had. But those are just my opinions.

Let's be honest, most of us don't need the A-number-one-best, even if there were such a thing. There's more than enough wondeerful chocolate in Belgium that can do the trick.

Just try them out all.
Good reason not to try to do Belgium in one or two days.