Gunstar Heroes, Streets of Rage 2 and Shining Force are definitely worth the new $5 price.
Funny, I saw about the PSN sale and tought: can you imagine if Nintendo allowed something like this on Wiiware or VC? I woudl think that sales would pick up not only on the discount titles but on others as well since everytime there is a sale on PSN or XBLA you end up picking up a game not on sale because you're already there or noticed a game you forgot had released (as for me, I'll be getting the Valkyria Chronicles DLC on sale).
Best of luck to Sega. Hopefully sales of all Sonic games on PSN, XBLA or VC will make them see what type of Sonic game we want next...