I've been collecting...
...since about 1997, and I've got about 150 of various makes.
My favorite is the first one I bought. It's a Parker Duofold, ca 1928. The nib is the best I've ever used. Right behind it is a Parker 51 "Flighter", made in 1951, with a broad Italic nib. I also have some modern Duofolds in Red Jasper, Blue Lapis, Pearl, Black, and "Orange". While they have great quality, they still don't write like the originals, even with 18k gold nibs.
I have some modern Mont Blancs, several Auroras, Pelikans, and Bexleys. I own several Parker Vacumatics, in Duofold and 51. They're great writers, but don't have the springiness of the older Duofolds. I also like Moores, and I have several Gold Medal and Gold Bond, and Diamond Medal pens, which are pretty generic, but excellent-writing pens.
Sheaffers are also a part of my collection, and my taste runs to the PFMIII's, and the older senior-size Balance pens. Of these, I really like a carmine red Balance. It's a superb pen, but it seems that the Balances from the later 1930's have stiffer nibs than the older ones.
My taste in ink runs to Aurora and Pelikan. I never really cared for Parker inks. Waterman is a close third.
There is absolutely nothing like a fountain pen from the 1920's and '30's.
Here are a couple of my favorites - Top is a Sheaffer Senior Balance, rare carmine red. Bottom is a Wahl Eversharp Deco.