Lets get this started! This twitter account is official and responds to users.
@SEGA Release [Insert games you want here] on PC! #SegaPCPorts
I cannot find a reason for any of these titles to not be on the platform.
Bayonetta - There is a dearth of character action games available right now and Rising, a Platinum game in a similar vein to Bayonetta, was the top seller for 48 hours during the Steam sale on its debut.
Vanquish - 120 FPS, do I need say more?
Valkyria Chronicles - Strategy RPGs are the platform's bread and butter
Resonance of Fate - The FFVII and FFVIII releases on Steam have sold quite well despite not being the best of ports and so late. The battle system for this game seems well-suited for higher frame rates.
Feel free to request other Sega games as well, there are plenty of contenders so pick your favorites!
Skies of Arcadia
Panzer Dragoon Orta