Borderlands was released in 2009 and was pretty popular and cool, receiving an average score of 85 percent gamer satisfaction according to Wikipedia. The one major criticism was lack of character skills. In Borderlands 2, the characters are intriguing. The graphics for the different levels and the design of the weapons are really amazing, and almost realistic, reminiscent of Bulletstorm.
On a scale of 1 – 10, the difficulty is a 6 or a 7. The missions are a bit confusing the first time you play the game. For example, on the road to Sanctuary, you are trying to find Corporal Reise who was attacked by Bloodshots and is M.I.A.  You may find yourself wandering all over the place until you find the enemies that are attacking him.   
The game starts out with in the future on a planet named Pandora.  The player picks one of the Vault Hunter characters, Axton, Zer0, Maya or Salvador. In character, the player follows a little robot, named Claptrap, who points out dangerous enemies that the player will ultimately destroy or kill.  Claptrap is helpful, but can be noisy and annoying.
    Axton is a commando character.  He summons sable gun, which shoots armor piercing ammunition at the Psychos.  They are enemy bandits who want to kill humans.
Zer0 has deception skills. He is an assassin capable of creating a decoy of himself and becoming invisible for short periods of time.  This helps him unleash critical hits on his enemies with swords, guns, and sniping weapons including pistols.  
Maya is a siren.  She has an ability called phaselock -which can suspend enemies in mid-air.
Salvador is a new character to the Borderlands series, and he is a gunzerker; he can dual-wield any combination of guns.
Vault hunter characters can be killed by being shot, blown up or stabbed with an axe.  
When your character dies, he or she respawns in front of the spot where you find a respawn machine-like a checkpoint.  You can respawn as many times as you die.
When you play Borderlands 2 as a one-player game, you are alone in the world with Claptrap and enemies everywhere!  Players fight the Psychos, Bullymogs, Skags and tons of other enemies out there.
The base game itself is about $60, but you can buy a game guide for the entire game for about $20.
If you enjoyed Bulletstorm, you will love this game as much as I did because the content of the missions is sort of similar in both games.  You hardly notice the soundtrack in the game because it is almost muted.  You do hear growls, sounds of the guns, screams of the Psychos, and the shrieks of annoying little midgets.  The sound help you know where the enemy is coming from, and it’s almost realistic and is helpful.  B2 is rated M because of language, adult content, alcohol use, and blood and gore.  Don’t let this stop you from enjoying the game.