I love the underdog film on the low budget that just blows you away with its wonderful self.
I love a psychological profile to be built of characters rather than car crashes chase scenes and explosions.
Two films like that (under rated and low budget) come to mind : Breaking Away and The Endless Summer.
It all starts with the story and script, to me. Low budget means that script better be good because they don’t have millions for CGI that is so glitzy and addictive to 80 IQ audiences.