>>63815457
The jet pack and being able to change levels quickly or get up to the vantage point you're being shot at from is fine. PA in 4 is nice in making you feel bigger and more imposing but the marine armour is the coolest.
>>63815472
>lonely game
Parts of 3 capture the magic of the first, like when going round bombed out ruins on the map in the first or if you revisit Necropolis and its all now dead. Travelling around by yourself on the overworld map is sort of similar but 3 does that better.
>>63815503
They all have their charms and drawbacks, but you even like 76? Shame that 76 isn't an offline game or I would play it for the map alone.