The last installments of the Mechwarrior franchise were Mechassault and Mechassault 2: Lone wolf, to the best of my knowledge. Mechassault I played and found to be extremely dull. Gone were the days of tweaking and building mechs, picking weapons load-outs and hoping you'd made the right choices. Gone was any sort of tactical choice in mech selection. You simply went into the mission with the biggest available mech. I didn't even bother with Mechassault 2 after 1 disappointed me so badly.
Armored Core 4 is the last one I tried (got the demo), but the Demo failed to wow me at all. I just couldn't like the control scheme (why is a common button like Y bound to something that has no apparent use? Sure, you move fast with the overboost, but you drain all further boosts and you HOLD STILL while charging). The demo went from easy fight, to easy fight, to ridiculously irritating fight that I just decided to drop the demo and walk away. As a final injury, I found that all the weapons were incredibly unsatisfying (you barely noticed some of them firing), and bound to flat-out WEIRD controls.
Chromehounds, from the same people that did Armored Core 4 is a much 'slower' mech game: these things don't inexplicably take to the sky, fly, and leap around: they stomp all over everything in a satisfying way, and the weapons feel mighty. I really like Chromehounds, and give it a recommendation.