I'm with you.
Even in the Ultimate Spider-man COMIC (which the Amazing Spider-man movie series seems to be more aligned to), Electro is yellow, bald and wears a black/purple-ish jumpsuit. He was originally a thug for the Kingpin. His look is not much different from the movie interpretation (with the exception of the blue color).
Ultimate Rhino is indeed a large military suit and is called R.H.I.N.O. In the comic, it's also had the huge 'roided out look of a man in a Rhino costume, just more armored and spiked up. In fact, it's operated by a nerdy, scrawny little guy who sits inside named Alex O'Hirn. Think of it like any character who sits in a big robot armor suit....Gundam, Pacific Rim, practically every Japanese Mecha anime, etc.
It's just a bunch of people who can't keep their minds open to different interpretations and perhaps have not even READ the Ultimate Spider-man comics and are familiar with the Ultimate interpretation. I think both these movie interpretations are fine and I think they'll work well for the flick. With all the hate that these villains get FOR HOW THEY LOOK, I don't understand why fans seem to ignore more "critical" changes like the MCU's African-American Nick Fury (also based on the Ultimate universe comics).