"I get it, this is not a great movie, but it's very entertaining and has great visual effects."
"Entertaining" isn't the same as being "good". In terms of the difference in rating between "Pacific Rim" and "GINO", one is a love letter to kaiju movies of yesteryear that also had a compellingly textured world, with some good actors. The other was a bastardization of the original movie and the character itself, a movie that borrowed wholesale from other much better movies such as "Jurassic Park", "Aliens" and "Star Wars", having more to do with those than the series it's based upon, all done with a very cynical attitude.
"Definitely doesn't deserve 5.3, that's for movies like Batman and Robin"
DEFINITELY not. "Batman and Robin" was just awful, like one out of five awful.

Simply put, Pacific Rim is a better made movie.

Perhaps because Pacific Rim was original
Yet it borrowed a lot of plot elements from "Independence Day".
Mr McGee, don't make me angry. You wouldn't like me when I'm angry!

Perhaps because Pacific Rim was original and paid homage to classic kaiju films and this film was nothing short of stupid and a slap in the face to Japan.