I can't argue with that. Mechwarrior 3 felt a lot better than 4, although I do prefer 4's torso-twist that can be controlled by the mouse. But 3 has a better story in my opinion. (although the sudden change from antarctic ice to a fricking volcano near the end is kinda odd.) And it was so much fun to load up the biggest mech you could get with a huge load of ER large lasers and just pop everyone's legs in a furious barrage of coherent light. And then you had to wait for your mech to cool before you could do it all over again.
As for Armored Core, a lack of modern consoles means I've only played the very first generation. Now unlike what the vids for Armored Core 4 showed, the first generation features slower mechs with less guns, a much smaller targeting reticule, a very limited energy supply and far more indoors, up close and personal action.
This means that dodging is much harder and if you use energy weapons (like I do) you need to carefully ration the amount of shooting and boosting you do because you DON'T want to be stuck walking around on the floor for 30+ seconds, unable to shoot/boost, waiting for your generator to refill the energy bar. For some reason, once emptied completely, it won't let you use any energy untill it has completely refilled. So if that happens, you are going to get hurt. A lot. But that's why I like it.
Oh, and what's this old Gundam game you're talking about? I love Gundam and only the fact that it's stupidly expensive to import stuff from Japan has kept me from collecting things related to it.
(By the way, radar and the like are said to be scrambled by the Minovsky particles that are thrown out by every single military vehicle, at least in Amuro's universe. So the argument is that they can't use tracking weapons. But, that admittedly shouldn't rule out heat seekers or image recognition.)