If I could only have one rifle......I'd be very bored.
For years, I had one rifle, a .257 Roberts I inherited from my grandpa. Well, I had a .30-30 Savage M340 for a while, then sold it to my Uncle. I used that .257 when I went deer hunting...period. However, came the time I started thinking about New Mexico hunting. I decided if I were going to hunt elk, I needed a bigger gun. I bought a Savage in 7 mag. Now, the elk hunt fell through and the only thing I ever shot with that Savage was 4 whitetail and a New Mexico mulie. I spent 200 on that Savage and about 200 on scope and rings. I fell into a Weatherby 3x9x44 supreme sell out for 150, HECKUVA deal! Fantastic scope, compares with 400-500 dollar scopes.
So, then I had a .257 and a 7 mag. I had been reading about this Remington M7 stainless and really wanted one in .308, what I consider the perfect all around Texas/New Mexico hunting rifle/caliber combination. One day, I won a Remington BDL in .25-06 as the door prize of a local gun show I went to. I picked up the rifle and ran down the street to another gun shop to ask if they had a M7 stainless in .308 and would they consider a trade. They did, we did, and I had to spend 300 extra bucks on a scope and mounts, but I got my dream rifle and have hunted with it, killed multiple hogs, deer, and coyotes since then.
I also have a sporter SKS that's pretty worthless, but is fun at the range. I have a .357 lever carbine basically for the same reason. So, I feel I have three NICE rifles, very accurate, and can cover ANY hunting situation with that caliber selection from shooting prairie dogs (we don't have any) or coyotes with the .257 (or deer), to elk and larger game with the 7 mag and I pretty much have shelved both of those rifles for the last ten years because I have this perfect hunting rifle in the Remington M7 in .308. So, what's wrong with having even MORE rifles if you like rifles, are a rifleman, bury yourself in ballistics tables, what not???? Hey, don't like it? It ain't against the law to own more'n one gun, ya know. When it becomes such, I'll move.
BTW, for investment, go with milsurps. My 80 dollar Hakim is worth at least 400 bucks now, I'm told. Wish I'd bought a couple hundred of 'em. LOL I can tell ya this, if I made a lot more money, I'd have a lot more rifles, shotguns, handguns, .22s, milsurps, you name it.