Ok, let's face it. The Warriors franchise is the Madden of non-sports gaming, and by now it's unlikely that any well-informed gamer is still sitting on the fence about the whole affair.
So you don't waste your time, I'll get to the point: if you hate Dynasty Warriors, Dynasty Warriors Gundam 2 will not change your mind. Ever. No patch, no DLC, no Xtreme Legends expansion, and nothing I can say will get you to like it. It might be a prestigous cousin to the greatest videogame series ever, but you don't care, and Dynasty Warriors Gundam 2 will give you no reason to.
Full disclosure: I call myself a Warriors fanboy, but I only really devoted significant play time to Dynasty Warriors 3 (and its Xtreme Legends ripoff pack) and Samurai Warriors. I quit playing Dynasty Warriors 6 for largely the same reasons Jim did. I'm also a Gundam poser. I know more than the average person about Gundam, but most of what I know comes from episode synopses on that ever-useful resource for mecha posers, MAHQ. I never actually played the first Dynasty Warriors Gundam, so most of what I know about this game is probably old news to veterans. I did watch most of Zeta Gundam (until Animax stopped using subs) and the first season of Gundam 00, so I guess that counts in some small way.
Now, once true Warriors fans get tired of kicking my pelvis, I'll get into the reasons why I think Dynasty Warriors Gundam 2 is one of the best, most fun iterations of the formula yet:
There's a big difference between big stompy robots and ancient Chinese warriors, and it's not the frilly sleeves (some of the robots have those). It's the verniers. Having verniers means having jetpacks, and everything in Dynasty Warriors Gundam 2 has a jetpack attached to it, which means that these big stompy robots can stomp real fast. Now, pilots get their take-out food home before it goes cools, which means it tastes better and improves morale.
Jetpacks are also the lynchpin in a great combat system that makes the game action even more intense, but that's really just a side bonus, because warm food is more important than intense combat action. Unlike the core releases' recent renbu system, Dynasty Warriors Gundam 2 uses "boosting", where you can chain together strings of attacks for as long as your thruster gauge allows. So rather than trying as much as possible not to get hit (which would decrease your renbu meter in DW6), you're encouraged to charge into the thickest concentrations of enemies, chaining combo strings by hitting the boost button, which also shrouds you in a convenient body-slam forcefield for extra mayhem. When you're in danger of overheating your thrusters (which would break the chain), you can interrupt with an SP attack (aka musou), which gives you breathing room to recharge in the middle of the animation. And since the SP gauge refills automatically when you're at low health, it's actually quite exciting, blasting through crowd after crowd, seeing how long you can go at critical health before you have to break off to find a meat bun.
Stompy robots don't need no stinking gates!!!
Expanding on the "everything in Dynasty Warriors Gundam 2 has a jetpack attached to it" bit, Dynasty Warriors Gundam 2's locations are subdivided into fields. Each field is pretty big and acts as a spawn point, which means that as soon as a heroic pilots enter a field to conquer it, innumerable hordes of grunts just fall right out of the sky to stop the invader. Friends, we are free. Now, in this age of freedom and jetpacks, we can come to the battlefield from any direction, be that up, down, or somewhere else. It's like the end of slavery, but with beam sabers.
Even bigger stompy robots!!!
This has actually been mentioned before, but bigger stompy robots are so big they get double the coverage! And they are big. They shoot big beams, have big verniers, and kick dudes around with big feet. They've got funny names, like "Big Zam", and are piloted by people with funnier names like "Four", "Ple", and "Glemy". When people and the things they pilot have names like that and can take themselves totally seriously, you know there's a great amount of emotional depth and complexity in there.
Robots can get their arms chopped off!!!"
Dynasty Warriors games are, sadly, rated T for teen, which means you can't show ancient chinese soldiers spilling their blood and guts out whenever a dude pokes them with a pointy stick. Thankfully, stompy robots face no such limitations. In fact, they're so happy about it that they run straight at your beam sabers to be dismembered, their arms and legs flying apart like props in a Monty Python sketch. Heck, even the game's intro movie begins with a rain of burning robot bits. Bloody mess, sans blood (oh well, can't have it all).
Just as you could find out what would happen if Shu won in the end in Dynasty Warriors, Dynasty Warriors Gundam 2 shows you what might happen if you actually managed to rescue the Radish, or if Strike Freedom Gundam and Infinite Justice Gundam got into a fight with Master Gundam and God Gundam. You might not give a rat's ass about who those actually are, but I think you can agree that those are some pretty epic names for stompy robots.
If you thought having 19 mobile suits to screw around with was a lot way back with Dynasty Warriors Gundam, the sequel really piles it on. Now you have frickin' 64 stompy robots to stomp around in! Gundam fans who aren't disgusted about the plot butchering (seriously, lighten up guys) can enjoy suits from Char's Counterattack, Victory Gundam and SEED Destiny. Ok, it's cool to hate SEED Destiny, but that Strike Freedom Gundam has a whole lot of beam cannons, which can never be a bad thing.
Further, there are no clones here, because cloning is immoral and should only be be used in the service of very specific and worthy causes. While every attack is performed the same way, no two attacks are exactly the same, because no two mobile suits are the same, not even the ones that might have been simple palette-swaps in a lesser game (i.e. Gundam Mark II and Gundam Mark II Titans version). More uniqueness can be slathered onto your mobile suits by switching out pilots and adding passive skills to the mix.
What's more, Dynasty Warriors Gundam 2 is no snobby elitist club exclusive to the Gundam bourgeoisie. If you want to connect with the average everyman cannon fodder unit, you can! By working hard and collecting parts you too can feel the satisfaction of being one with the people through piloting a Ball.
It's so awesome that they won't let you have all of it
Publisher Koei has realized that they created a game too great for fools to comprehend when they pasted Gundam and Dynasty Warriors together that second time, and they were afraid. So afraid, in fact, that they tried to neuter the game by denying non-Japanese players the aural joy of Seki Tomokazu's voice and inserting terrible English-language voice acting. They also tried to convince us that the game was bad by allowing many of the fodder robots to have cheap knockdown shots or making the boss fights last for much longer than they should. They even tried to water down your fantastic critical-health boost chains by adding a very slow flow of tiny-damage attacks that whittle down your health to force you to leave the field earlier than you should have. They tried, but they failed. Dynasty Warrior Gundam 2's majesty shines past its terrible voice acting, and delivers a devastating blow to the blatantly inferior Killzone 2.