For playing legacy games, I find any of the NG systems a grand waste of money, and I say that as an owner of a SAM system myself. I love my SAM, but I'd find it lunacy to buy one to try and get my legacy Amiga fix with.
For games, a lot of the time you end up having to use UAE on that fancy PPC NG Amiga to run said game, and $3000 is a lot of money to spend for a niche system when a Windows box with WinUAE is pretty much a commodity.
Of course, many older, legacy games and programs will run natively in OS4. Many also will not, and you'll end up having to "emulate an old Amiga on your expensive NG Amiga". I'd have a hard time spending much money on that, but YMMV. That being said, legacy app support on OS4 via UAE is great, just a point and click affair.