One of the funniest games ever made.
Let me get the easy and mandatory stuff of the way:
Okay so this is the same engine as 3 years ago. However, there are improvements, at least on the PC version. The physx is now able to display some cool visual effects. The improvements include
+hundreds of sparkles from explosion guns;
+ fire looks like fire now;
+the corrosion goo now oozes out on the ground and cascades down the slopes;
+ the battlegrounds are now littered with pieces of rocks and gravel (that do not disappear by the way);
the electric guns now display more sparkling effects;
+there is now some sun glare
+there is now aurora borealis
+there are some nice snow and desert effects
+the anti-aliasing has been greatly improved
+the day to night shift has also been improved
-the water looks pretty much the same though
-we still get Directx9
-Visually, everything about the game has been improved except that you still cast no shadow and you still can't see your legs
-The Resolution problem. okay so I thought I was playing with my native 1920x1080 resolution until I figured out (at level 10) that you needed to change the resolution one more time IN-GAME. Apparently, changing resolution in the game menu does squat. So I've been playing the crappy console 1080x720 whitewash resolution for about two hours before I figured out what was wrong. DON'T MAKE THE SAME MISTAKE.
-SLOW texture loading, just like in the first game. Whenever you enter a new are or go into a shop it will take a couple of seconds for textures to load. Thanks consoles!
Okay as for the gameplay:
It remains largely unchanged however there are improvements. The sprint effects are now more realistic. One of the things I liked is that it is MUCH MUCH harder to earn money now. I reached level 18 and rarely had more than $ 1500 bucks in my pocket. This is a breath of fresh air considering that you could easily rack up $ 200,000 by the time you hit level 15. ( I am not even mentioning the exploit of cloning artifacts and rejoining friend's game to essentially have infinite money). Also, I should mention that they now got rid of all those unnecessary zeroes, as in, there really is no reason to sell a gun for $ 254,620 when they could downplay the entire currency by a factor of 1000. Ergo, you would have to buy the gun for $ 254 instead.
The skill tree is somewhat the same from the first games with some similar perks.
They now added Eridium as currency, which is rare. Except you can only use it to upgrade your ammo/grenade/backpack capacity.
They haven't changed the driving. It is still a keyboard+mouse driving which still sucks.
They also now added caravans which can get attacked and then get looted for rare weapons.
The elemental effects largely remain the same. Fire is good against flesh and corrosion is now really effective against armor (robots don't have shield or health anymore, only armor). Also, robots are easily taken out when their limbs are blown off.
It seems like the auto-assist weaker than in the first game but it can still be felt.
The enemies are even more hilarious now. The voice acting is great (same goes for THE friendly NPCs), especially when you hear the midget armored goliaths talk. It's obvious they try to overcompensate for their vertical challenge by being extra badass. The enemies still do the barrel rolls, they still take cover and can spend up to 5 seconds and they can also jump from platform to platform. There are also the buzzers (make-shift propelled helicopters much like in the mad max movies) which are pretty fun to shoot down. It's even more fun when they sing the Ride of the Valkyries composition (from Apocalypse now), it's pretty amusing. Some midgets ride on each others' heads too.
I'm not too sure about the insects though. They are gross and disgusting to fight.
In general, it is still way more fun to fight humans or rather, the humanoids, rather than the robots and the beasties.
I'm not sure if it's me but it looks like they put more effort into adding more flare to almost every other gun. The seemingly random-generated stats are still there but at least gun skins look more flamboyant and peculiar. They also varied the standard appearance types somewhat. So, not every rifle gun is necessarily elongated for instance.
It's a continuation of the first story (perhaps a couple of years after opening of the vault) wherein The Handsome Jack, who is in charge of the Hyperion Corporation is attempting to open an even bigger vault and obtain control of the prehistoric monster to rule Pandora. The story has some twists, surprisingly and it's always welcome to see the good old friendly NPC's again.
In the end, perhaps this could quality as Borderlands 2 since it's a continuation of story and all, I just didn't really feel like it was a new installment all that much, a lot of things feel same, although it's a definite improvement over the old one. There is more narrative, more quests, new enemies, new artifacts, mods, etc. etc. But there is not necessarily more depth, perhaps it is so because of the type of game itself. However, there are plenty of comical and satirical moments that catch you off-guard. The game is also littered with easter eggs.
If you're still not sure, then simply think of this, you are getting a lot of content for $ 60.