Armored Core 2 expands the Armored Core formula and greatly improves upon it with smoother gameplay, greatly improved graphics and performance, new music tracks, and new mechanics and features to enrich the experience of playing. The story is also interesting, with various corporations and factions fighting for dominance on Mars, with your character playing all sides in the conflict up to a more linear set of missions near the end. The game also calls back to the PS1 AC trilogy a lot in both the arena and main missions, which is fun to see. The Arena and missions in general have seen a lot of balancing done to make them more friendly, although I'm sure the Hard mode available at the start makes it all as tough as it ever was. Not sure since I played on Normal.
This is probably the most bland review I've ever written. There's nothing all that weird about the game (other than its slightly abrupt and confusing ending, which I won't delve into), so there's not much to comment specifically on. It's a continuation of the PS1 series into a new generation. Not much to say, but it sure is good!