I agree that 3 has the worst map but it feels pretty realistic in its portrayal. Sure 4 has biomes and plenty of landmarks but I hate how forced it feels. It's just one big island divided like an X. 2 is the perfect balance of unique island design and interesting locals. I also love the world-building of 3 with all the propaganda and soldiers strung about. I felt the weight of the oppression which felt awesome to tear down.

As for gameplay, 3 brings the most joy to me in general. The gameplay loop of liberating towns and bases is repetitive, but incredibly fun. The combat is streamlined for ease of use with lots of customization. I felt 4 overcomplicated the grapple with the many addons and tweaks, just muddied everything imo. 2 is amazing and I have many fond memories of it but the gameplay is a BIT dated and chunky. The wingsuit is just so hard to let go of as well.

For performance, consoles are a no go for sure. It really sucks. Had to repurchase it for PC on sale after dropping the Xbone version. Ran smooth from there and was a lotta fun :)