I want to expand my Marvel titles because as of right now I only collect/read X-men, picking up X-Men #7 tomorrow. 
 
Any good titles?
 Is New Avengers better than Avengers?

Favorite characters? Writers? Artists?  
 
All three Avengers titles are sort of mediocre to me, and I expect more, but main book has been heating up last two issue, New is good with team interaction, and Bendis writes those characters better, puts more emphasis on them, Avengers its more plot.  
 
I am a huge fan of the Thor minis out now, Astonishing especially. T-Bolts is quite fun. X-Factor is always boss. 

X-Factor and T-Bolts are always a good choice.

My favorite marvel books:
 
Captain America (Brubaker)
Invincible Ironman (Fraction)
Thor (Fraction)
Secret warriors (its about to end though)
Fantastic Four (Hickman) Soon to be relaunched as FF
 Black Panther

Iron Fist is always good
 
T-Bolts is good 
 
And as Nighthunter said above Fantastic Four is amazing, as is Captain America.

Uncanny X-Force. One of the best Marvel titles out there. And certainly worth a look if you're already enjoying X-Men.
Amazing Spider-Man's looking pretty good since Big Time started.
Invincible Iron Man has amazing writing and artwork, but it's got to be your cup-of-tea, or else you probably won't enjoy it that much.
 
Avengers is pretty good, but the artwork isn't appreciated by just everyone, so there's that downside.