The price point might be tough for people. I think you can buy original NES systems for less. They aren't going to be HDMI compatible, but I think those adapters will run you $20 on Amazon.
proper lag free upscaling isn't that cheap.
Furthermore, original hardware can be finicky; the NES has a notoriously unreliable connector for reading carts and requires a bulky AC adapter. Meanwhile, the AVS has an improved design, new/clean cart connector and runs off 5V from a USB port on the back; most people can plug it into their TV, receiver, or any other device in their entertainment system with a spare USB port (like an Xbox or PlayStation).
It's a superb value for someone with the cash to burn. I own both the NES and the AVS and think both are fantastic, but would recommend the AVS to friends and the NES to purists.
A Link to the Past: Bought for $17.56 about 5 years ago, and it seems that I'd be paying around $45-$50 to get it now.
Zelda 2: Adventure of Link: bought for about $5 in 2010, selling for about $15 now.
Oof! This one's the biggest jump I've seen so far. Metal Warriors on SNES. I bought that in 2009 for $40, and the cheapest listing for it on Amazon right now is for $200.
Could be. The front loaders tend to wear out their cart connector due to the weird VCR loading mechanism. It's easily fixable now but at the time it probably doomed them to the trash.
The top loaders were always sorta rare because they came out way late in the NES's lifetime (post SNES and Genesis) and IIRC only sold for a couple years.