Acidic strength comparison between sulphuric acid and nitric acid
The important thing about acidity is the stability of the conjugate base, which is enhanced by resonance effect and inductive effect. The more stable the conjugate base, the easier deprotonation becomes, and thus the stronger the acid. 

In a $\ce{NO3^-}$ ion, the negative charge can delocalise among three O atoms, but in a $\ce{HSO4^-}$ ion, in addition to delocalisation among three O atoms, there is an additional OH group, which further stabilises the anion by inductive effect. So $\ce{HSO4^-}$ is the more stable conjugate base, and $\ce{H2SO4}$ is a stronger acid than $\ce{HNO3}$.