Originality is important, condition then depends what you want but the better the condition the higher the premium it will demand. Condition holds value the higher it is. Then there is rarity.
Some rifles do have an appeal if new. I tend to think that starts from about 1980, just because modern manufacture doesn't always stay looking good once roughed up. Patina or tatty???

Well I had 40 plus rifles, and another 40 to get them, but now I have about ten. I only need to shoot about five to quench my need for shooting, as so many I found too similar or just not up to my tac driving love.
Other collectors have a completely different take. One of every kind and model. Only the most beautiful. Whatever floats your boat. Some twenty of the same rifle.

Best bit is whatever your angle, rarely do you lose anything. Maybe less of a return than money in the bank but at least not a loss. Most of the return is just the enjoyment each one gives. That will do me.