They're not. TOS has 6 movies, and two good ones (TVH and TUC)
TNG has 4 movies and two good ones (GEN and FC)
TNG has a BETTER ratio, if anything. And frankly, nothing in INS or NEM touches the cartoonishly forced plot events of TWOK or the juvenile idiocy of TFF (although Insurrection tries, on that second one).