You need an NTSC to VGA converter. Many de-interlacers and video processors perform this function.
Some I am familiar with include:
Instant TV by Aims Lab -- Discontinued but may be found on eBay for about USD $60. Has TV tuner.
Any of the DVDO iScan models, together with a VCR for a tuner Priced from about $200. for an older model on eBay which will blow away the Instant TV, to a deluxe model for about USD 1000.
A Lumagen Vision, cost $1000. scales the video to the pixel dimensions of the LCD monitor probably better than the monitor itself taking in the output from the above models. Needs a VCR for a TV tuner.