Rurouni Kenshin is a classic here in Belgium/France, it's one of the best samurai based series, and, to give you an idea, apart from the nearly 100 episodes (I'm in the 60s right now), it also has a lot of video games adaptation and OAV. You should take a look!
The last anime I watched was Gungrave, it's also an interesting anime which resembles the Godfather (a bit slow until the episode 14, but darn good after.)
And I guess if you like Cowboy Bebop, you'll like Samurai Champloo, the same peoples behind both projects, and both have GREAT soundtracks.
I've takent note of Kaiji and Golden Boy, Golden Boy I didn't knew at all to be honest, but my little bro has already watched Kaiji. Here his list, he watched more than +200 animes and is currently following +10 at the same time (keep in mind that some animes just have 13 episodes though, and on the list 'movies' or OAV are seen as 'animes' too)
http://myanimelist.net/animelist/gothx
EDIT:
He gave 9 to Kaiji! That's rare of him

And to compare: Samurai Champloo 7, Rurorin Kenshin 7, Cowboy Bebop 8.
Gave 10 to GTO (I LOVED it too, watched it some four times!), Seto no Hanayome (THE funniest anime I've ever seen!) and Monster (a bit more 'serious', a seinen, but till the 72 episodes you're into the whole thing...)