One theme I particularly like in media is psychological battles when two or more characters try to outsmart each other. This is probably why Death Note, Gyakkyou Burai Kaiji: Ultimate Survivor or One Outs are among my favorites... but not every show handles this aspect well, so let's list things a good series about gambling should have and why Kaiji (mainly the first arc) checks them all.
I think this goes without saying, you don't want to watch a battle only to find out the main character won only because he/she had hidden ace in ass or something.
Protagonist needs to THINK of a logical strategy in order to ensure his/her win, and it needs to be SHOWED. What's even better in Kaiji is that not only he is thinking, but also other characters at Espoir. It's not like our hero is some super intelligent Mary Sue that can outplay literally everyone, at some point others even get the same idea for a win tactic as he, they also cheat and lie which makes the whole game not that easy to win and more interesting to watch.
If your read Liar Game, where an explanation of rules for a particular game can take even a whole chapter
full of walls of text, you know what I'm talking about - not saying LG is a bad manga, it's just one poor aspect of it.
First arc of Kaiji starts with literally - Rock Paper Scissors (with some additional rules added), but when you
watch the show, you become amazed how complicated such simple game can become!
Because they increases the tension.
Is saying that a loser needs to pay off his debt by working as a slave in a mine enough
to convince you that a show has high stakes?
And there's a lot of that in it, the thrill of what to happen next keeps you on an edge of seat, especially that the main character does not win everytime.
Of course Kaiji is not only about gambling, there's hope, betrayal, desperation, recklessness, all accompanied by
goofy character art style that manages to colorize emotions in funnily exaggerated way, man, now I feel rewatching it.
And wait, did I mention there's no w*men in this anime? 10/10
ざわ･･ざわ･･ざわ･･