I find it amazing how even after the additions that came with the following games, all of them still fall short in comparison to the very first one.
This one has it all, an amazing soundtrack full of bangers (Heat to be filled with, All for one and Dead end are good examples), excellent voice acting, both in japanese and in english (well, Puru's is not always the best, but Kamille's, Jerid's, Scirocco's and Domon's are extremely good), beautiful maps (like the Mausoleum or the Satellite Elevator) and a fun combat system that isn't too fast, nor too slow.
The Official Mode is good and has various iconic battles from the original Gundam trilogy (the A Baoa Qu battle always left an impact in me) and the Original Mode... well..
It's simply amazing, a bunch of teams consisted of various characters from different Gundam animes. Good missions with great battles and fun and sometimes even emotional interactions. There isn't a single bad team in the game, but the best one is easily Domon's, consisting of Domon Kasshu, Milliardo Peacecraft and Elpeo Puru, it has the best moments, best battles and best interactions.
The only real complaint I have with this game is the outdated cutscenes (but that is more a product of aging than anything else) and the relatively short cast.
Unfortunately, the games with a bigger cast fuck it up. DWG2's battles consist of an RNG fest with few good moments, DWGR is also fun but it doesn't have the same charm, and I haven't had the chance to play DWG3.
This game was my childhood and it still holds up.