Are we talking about the movies or the actual comics here? Because the OP wasn't exactly clear.
In any case, both. Old Superheroe have been done a few (or many) times before for a reason, they have a classic "quality" about them, and as such fans like them, however old they are. Prime examples of this are Batman, Superman, Green Lantern (Hal Jordan version at least), Spider-man, and Iron Man.
New superheroes, while some can be innovative and well recieved, they tend to have much less "staying power" as their powers can be very gimmicky, or due to the new nature of the character, the writers don't know how to handle them. Another problem with new superheroes, that was especially prelevant during the early Nineties, is an attempt to be more extreme, and coming off as either a massive dick, or something of a joke.
Also, when do you count a character as being "new"? Deadpool and Hellboy have been around for nearly 20 years, but have only recently gained popularity. Do they class as "new" characters? Or it that characters such as X-23, ones created and published after 2000 only class as "new"?
In conclusion, while a mix of characters both old and new are good, the new ones will not have the same popularity as the older ones for at least 30 years after their first appearance.
/Comic geek