Original Versions of DMC3 and DMC4 Delisted From Steam
Capcom just delisted the original releases of DMC3 and DMC4 from Steam (if you already owned the games, you can still install and play them). The two games are still available to purchase in improved forms as Devil May Cry 4: Special Edition and DMC: HD Collection. I assume the old versions were delisted to ensure people would always find and buy the new releases rather than the old ones.
It's a small bummer in one way: though the original version of DMC4 has far less content, its performance was way better. But that doesn't matter today unless you're running really old hardware. There's also a few mods that were made for the original version of DMC4 that aren't compatible with DMC4: SE.
I'm not sure if there's any advantages to playing the old version of DMC3. The original DMC3 PC release was made by SourceNext who is infamous for their completely messed-up 2007 PC port of RE4 (which didn't even have any lighting when it released). Their DMC3 port was in a better state than their RE4 port, but it was still a basic port with some bugs.
If people want access to these old versions (at this point, the only big reason to get them is for the sake of collection), it looks like you can still buy Steam keys for them from some online stores. Here are links to stores still selling the games:
These games were also released physically (and these were real physical releases where you would install the game from the disc and run it, without needing to activate it online), so you can probably find the games on ebay.