Superman's powers are never, and should never be considered a curse.
The Man of Steel's powers are a blessing for 2 very simple reasons:
Superman's powers are controllable.
Even Superman's Heat Vision is controllable; he's not like Cyclops "cursed" to always wear a ruby visor to keep his uncontrollable Heat Vision in check, and to keep him hurting others around him for the rest of his life.
Super Strength too; Superman seems fine being able to gauge between using it when he's mild mannered Clark Kent.
Only time his powers are probably not controllable is when Superman sleeps; maybe then you could consider that a semi "curse" or a super inconvenience, but then again Lois Lane may beg to differ about that with her "experience."
The notion that Superman's multitude of powers are a curse simply because he now lives a never ending life of protecting the world (universe) fom threats is just... balogney.
To steal Uncle Ben's "With Great Power comes Great Responsibility" - this rings true for anybody not just superheroes.
Superman is the global protector, that is his calling.
Just like when a person becomes a new Father or Mother, being a parent is now your calling. It's a blessing, never a curse to be able to protect those that need protection and to defend the weak.
People who do that are heroes. These people will always look to them, to you as a "hero", their hero.
Being able to make a difference in someone else's life for the good is and always be a blessing.
Same with Superman.
Otherwise, why be a superHERO at all?