The competition between the two basketball players was legendary. Together, they made an impressive era for basketball...

[alpacinou]

Does it make sense to people "made an era"? Is this correct and natural?

The competition between the two basketball players was legendary. Together, they made an impressive era for basketball, one that fans of the sport will be talking about for years to come.

If that doesn't work, how can the idea be expressed?

 

[Barque]

Does it make sense to people to say "made an era"? Is this correct and natural?

No.

The period when they were both active was a great era in [professional] basketball.
The time when they were both active was a great period for basketball.

 

[jutfrank]

Do you mean something like this?:

The legendary rivalry between Johnson and Bird was era-defining, and is sure to be spoken about by basketball fans for years to come.

 

[alpacinou]

Do you mean something like this?:

The legendary rivalry between Johnson and Bird was era-defining, and is sure to be spoken about by basketball fans for years to come.

Era-defining, what a nice word! It's what I was looking for.

 

[jutfrank]

The basic collocation is: 'define an era' so you can play with the form:

definitive of an era
era-defining

'make an era' doesn't collocate.

(Note: Another really nice related collocation you may be unaware of is: 'usher in an era'.)