This is one of those discussions that will never fail to pop up (even in threads where it wasn't the original topic). I have opinions, as everyone else here has as well.
GEC is definitely going to take the lead when it comes to better execution of patterns, superior quality control, and a premium product offered at a decent price (the latter point is most certainly a matter of opinion and is based on one's individual perspective). GEC isn't infallible however, and there are certainly things that I criticize them on with regards to their dyeing processes, jigging, and some of their choices with regards to some of their finishes. Lack of stainless options doesn't bother me as I do not mind patina and generally take good care of my knives. I also vastly prefer good ol' 1095 over most of the 440s and their equivalents.
Case comes in second for me as I have some very good Case knives but I also have had some very not-so-good Case knives. I don't like their stainless steel at all but their CV is quite excellent. I don't like that everything seems to be "rounded" but that is simply me nit-picking somewhat. Aside from the garish covers, spotty QC, and limited CV offerings, you can still get a quality modern Case knife and they make for terrific users at a good price.
My experience with Buck slipjoints is limited to the standard 110s and the recent 301 we had made up for our 2018 Forum knife. Robust construction, no frills design, and very good stainless options make for a knife that folks shouldn't hesitate to put to significant and heavy use. However, they have a propensity towards leaving a lot of material behind the edges of their knives and therefore they make for less efficient cutters than the other offerings on the list.
I have limited experience with Rough Ryder (having only one). I think they are a good option to utilize when wanting to try out new patterns without breaking the bank.
US made Schrade is hard to beat for the value (or at least, used to be). Scarcity will always drive up demand as well as prices so most of the ones I come across will cost as much as a new Case or more theses days unless I get lucky at a garage sale or thrift store (happens rarely). I simply stay away from any of the new Schrade stuff - it's similar to Rough Ryder in terms of quality and it's entirely possible that they are manufactured in similar, if not the same, facilities.