Actually, getting the Laserdiscs or VHS are probably your best option, quality wise, as those are both in 4:3 (and are analog) and are sourced from the original (although with the Laserdisc, Warner Brothers only released Season 1 & 5 in their entirety, and then Seasons 2 & 4 only got half season releases and then I think they never got any Season 3 episodes out, so you get Standard Definition Broadcast Quality video on about 3/4 of the series that way) NTSC/PAL Masters. Columbia House Released the complete series on VHS---I'm not sure if Warner Brothers released the entire series on VHS by themselves through the regular retail chain. But I've got the regular Warner VHS of Midnight On the Firing Line/Soul Hunter from Season 1 (it's recorded in the SP mode, so it's VHS's highest quality), and when I compare it to the DVD, the VHS is the clear winner in terms of quality. Plus in the shot from Soul Hunter where Sinclair turns the cannon on the Soul Hunter and stands up, on the VHS Sinclair does not get cut off at the bottom of the eyeballs!
But with the data-rate, the DVD's were mastered at a variable bit-rate of about 4.5-5.0 Mbps (variable creates smaller files as the data-rate is always chaning, for example with a title on a black screen the DVD might only use 500kbps and then jump up to 7.3Mbps for a high-action scene and then down to a 2.3Mbps for a talking head scene, the stated Mbps is the average)with peaks going up to about 9.0 Mbps. Plus the DVD's use MPEG-2 compression, whereas Amazon and iTunes are most likely using H.264/MP4 compression at a bit rate probably around the 1.5Mbps (I was just looking at some videos that I have on my PS3, such as Mythbusters, and SD versions of shows are listed at 1.5Mbps H.264/MP4, while the HD versions are at 6.0Mbps H.264/MP4). Now then here's another issue, if Warner Brothers has given Amazon and iTunes files derived from the DVD MPEG-2 files, then they've compressed them from an already heavily compressed format. The Original Master tapes are Digital Betacam for both the 4:3 and 16:9 versions; Digital Betacam has a constant (with a constant data-rate, the Mbps only fluctuates by +-1 Mbps, so anywhere from 89-91Mbps) data-rate of 90Mbps; even if they weren't and the Original Masters were on DVCPRO or another Digital Broadcast tape, we are talking of constant Mega-bits-per-second of 25Mbps or more. So if Warner made H.264/MP4 files from the MPEG-2 files, then the video has already lost a ton of quality. Basically its like in the past, instead of going from the original master (i.e. Betacam SP) to another high-quality videotape (i.e. U-Matic) for duplicating to VHS, the chain was Betacam SP to VHS SP to VHS SLP (like what you would see on those cheap Public Domain tapes).
