I think I had stopped playing them by AC4. The original was great, yes it was a bit light on story by today's standard, but essentially you were a mercenary mecha pilot accepting contracts, missions each had their own story and there was a small overarching plot about 2 rival corporations fighting for power. Which missions you accepted determined which corporation took over the other, then in the end you discover life is a sham and the computers are controlling everything. Most of the games follow similar story beats, but there is a story progression between games and the mercenary organization evolves over time. The first 3 PS1 games,
AC,
AC: Project Phantasma and
AC:Master of Arena all follow the same mercenary (you) in a rebuilt society on post-apocalyptic earth. You could transport your saved game between them and keep all your equipment and human+ upgrades if you'd earned them, in fact some of the most powerful items in MoA could only be gotten if you had imported an
AC or
ACP game. The story was mostly a framework to customize mechs and the missions were mostly a framework to play around with your customized mechs, story was secondary
AC2 was OK, graphics were of course much improved since it was now on PS2 but they added radiators to shunt heat which I never felt added anything to the gameplay. Still a fun game.