The original was way more open ended than any of the sequels. Never played the PS2 port but you can just get it on Steam on GOG.

The original is, however, the best one, although it shows its age. Human Revolution is set before the original game and has very little in common with it, so don't feel you need to play it. I haven't played MD so I can't comment how much that story ties in with the original. Though they do keep it to a minimum for the most part in HR. You're fine just playing these if you want but some of the callbacks would be lost on you. Human revolution and Mankind Divided are set as prequels to the original game. It's a direct sequel and a lot of things wouldn't really be explained if you played it without that knowledge. I'd say ignore invisible war unless you plan on playing the original. I replied to someone above if you want to see what was different about it. The PS2 version, while functional, isn't really the optimal experience. However, I'd really recommend you play the pc version if at all possible (it'll run on almost any old laptop or desktop nowadays). I'd still recommend playing it if you feel like you can ignore those facts though, it's a good story and it really was one of the first of it's kind. That being said, for someone coming into it fresh in 2021 it's going to seem archaic, clunky, and ugly (the game wasn't a looker even at release.). One of my (and many others) personal favorites of all time.

Deus ex order to play