The points have basically been made, I'm just seconding/thirding/zillionthing them. Mainly, the customization has gripes, there was practically no immersion (feeling of moving in a heavy mech; slight delays and accounting for momentum and moving enemies, and powerful but sluggish stomping just weren't there), and the voice acting was terrible! The main character had lines like a bad-@$$ but he sounded like a sheltered dooosh.
Plus, they ruined a lot of the mechs in terms of how they're supposed to "feel" and behave in battle. I went straight for my beloved Timber Wolf (Mad Cat), and found it to now be a slow-poke, especially in the chassis-rotation. It's strength was always its ability to close in quickly and pick a range to start shooting, and to use strafing and circling to dodge and weave. But in MW4, it was like a crawling tank. And the kicker was the inability to install jump jets anymore!
In MW2:Mercs, I used to sacrifice main speed for the jump jets, which I could then use along the ground to slide quickly to the enemies and give 'em what for (I still had my chassis rotation, so it was all good)! Or in proper environments, just use its default maneuverability without jets to brawl them into submission. Now, all it could do was crawl pitifully, hoping and praying the enemy would come into range on its own, or resort to sniper configuration.
Sure, the MkII could have jump jets, but it was SOOOO SLOOOOW on the ground that it just wasn't worth it!
The weapons' effectiveness and damage type wasn't even right. The PPCs especially suffered from imbalance of risk vs reward, when before it was a satisfyingly damaging and impressive-looking blast, with carefully-weighed risks involved in using it. In this game? Just another average gun but harder to hit with.
Not being able to depend on a mech's canon characteristics is the biggest blow against a game's credibility, in my opinion.
(Disclaimer: All this is off the top of my head after YEARS of not playing, and I have memory problems, so feel free to correct me if I'm wrong. But those are impressions that seem firmly imbedded to me)
Edited by Audrey Byrne, 24 February 2012 - 10:04 PM.