Sonic the Hedgehog turns 20 on June 23, while seminal shooter Quake celebrates its 15th anniversary this week.

Intended to take on the might of Mario, Sega's Sonic first burst onto the home console scene on June 23, 1991, with Sonic the Hedgehog for the 16-bit Genesis and Mega Drive.

Quake, published June 22 1996, popularized several features that are now considered standard for first-person shooters.

In particular, players were able to use a controller (in this case a computer mouse) to look around, and online multiplayer became increasingly significant.

Sega are marking Sonic's 20th anniversary with the release of a downloadable Sonic Generations demo for Xbox 360 and PlayStation 3 - the demo vanishes after 20 days, pending the full game's release by November 22.

Id Software, the studio behind Quake, are hard at work putting the finishing touches to Rage, the first entry in only their third major franchise and due in October.

Id co-founder, technical director and (geniune) rocket scientist John Carmack found the time to tell BethBlog that Quake's online multiplayer "was almost an accident," but took off in spite of early technical imperfections.

He also reminded readers that the game's easily modifiable nature means that "many of today's industry greats trace their start back to working with Quake."

Watch the Sonic Generations trailer at
Read John Carmack's thoughts on Quake and see footage from its 1996 launch at