The thing most people also have to take into account is the setting placement and related design aspects. I was a bit blunt with the initial assessment, but outside of a corny comic book, where would you find 40's gangsters in a dark piece of science fiction? New Reno, with all of those aspects, was more of the corny "any easter egg goes" near-catastrophe of Fallout 2.
The number of the guns were mainly what was wrong. The .223 was used once, had a remarkable presence in Fallout, but was used ad nauseum in Fallout 2. I would, at best, accept that at the time of Fallout 2 that perhaps one or two Thomson's made it through the years. There was a reason why many of Fallout's guns were nondescript generics - mainly because some had obvious signs of wasteland repairs on them in order to make them function. FOT had a number of guns shit out from a WWII antiques store for no other reason than the year is +2170 and MicroForte had the science fiction style off. The number of misplaced guns in that was just simply amazing as they seemed to believe the science-fiction style was that of the 40's. Generics, with the weapons that a 50's-60's science-fiction comic/story writer would would dream up of and later make into popular imagination (take a look at some of the ray guns and etc. from that time).
All futuristic weapons in Fallout were based on clunky technology as if the works of Russell Ohl, Walter Brattain, John, Bardeen, Mervin Kelly and Bill Shockley never happened and the world developed from a logical extension of Lee De Forest's application of vacuum tubes. I am quite disappointed in the number of topics that lean more towards Counter-Strike than exploring that aspect of the Fallout universe. Then again, the whole setting thing seems to confuse many people, especially when it comes to F

OS. Oh, wait...FOT. No, wait, F

OS! Ah, hell, they're both shit, different grades of shit, and known for that due to very good reasons that mostly involve skewing the setting style.
So, to better state my previous, perhaps one or a few token guns, but beyond that is pushing it. Keep it to something like the Desert Eagle. Since that didn't really fit into what a 50's science-fiction writer would write in, I tend to think it is from someone in the senior aspect of the development team wanting it in and be damned anyone who doesn't agree, or a token piece for some particular reason that may be forever unknown to us unless said developer(s) speak up about that aspect. Either one does make sense.