Depending on your region (I know you already filled in Michigan), the VIC-20 may be a bit hard to come by. I've read that in the UK, it is almost uncommon and fetches surprisingly good money. Some people consider it a "decoy", a cheap computer Commodore shelled out while working on the "real" entry in the home computing business. I strongly disagree this was the case: Commodore already from the beginning wanted to get a foot in the market, and rather due to the VIC-20 did sell well, they had reason to release an improved computer. It would be stupid to produce a place-holder computer if you didn't know if you will be able to sell it.
For that reason, the VIC-20 is Commodore's first home computer with sound and colour graphics. Whether it will be valuable in 20, 50, 100 years time we don't know. The C64 however will be more famous and sold in those enormous numbers, which perhaps makes it an item almost everyone want to have. As pointed out, neither is really uncommon so collectors of today or in five years time will not put much value to them. I don't think the Intellivision is neither, in case you're asking.
I own all three systems, and frankly out of those Intellivision games I've played, I'm quite a bit disappointed. Some are reasonably good, but many of the early games are truly horrible, like a type-in Basic listing with slightly improved graphics. I know many VIC games are rather bland too, but I think within the selection of cartridge games (thus once upon a time more expensive to get), the VIC may have more playable games than the Intellivision. Maybe I just had a bad selection of games and am making an unfair comparison though.
By the way, if I compare the Commodores from a programmer's point of view, I prefer the VIC-20. It is more limited in graphics and sound, but has bigger characters and is more of a challenge of getting anything decent done than the C64 which is quite over exposed. Anything you develop for the C64, someone else has already done a better version of while the VIC still is a bit more like breaking new ground.