Ive kept nearly every species I could in the 20+ years ive been keeping fish and in my honest opinion you cant beat an oscar.
Love my midas too mind!-)
If I had to choose a favorite individual I had from the past, it would have been my male Nandopsis haitiensus, at about 8" tall and 14" long, he had more personality than many dogs.
But at the moment I have a shoal of Astatheros rostratum that are very interesting, and at 2 years just beginning to color up, and show personality.
as far as old world, any of the Paretroplus from Madagascar
among cichlids my current favorite is my current male 12" amphilophus amarillio. he's a glass banger
and will bite and head butt your hands/arm when in the water for what ever reason and will try when near
the water surface lol he thinks he's a bada... but his bites and headbutts are ticklish hahaha lol
My haitiensus male and female would draw blood when protecting fry.
They would tolerate no other tankmates in a 150 gal tank.
The Astatheros rosratum are what I consider the Central American equivalent to Geophagus.
my doviis, i waited so long to get them and chased around to get young, now they spawn all the time i shocked i couldnt get some quicker. but now i can sit and watch them for hours going about the couple life having little tiff and then making up lol and if one of the few others in the tank (plecs) makes an appearance their attention its drawn straight on it, parent to killer instinct is mental.