I purchased Sonic Riders: Zero Gravity for the Wii a few days ago, and unlocked two tracks called 80's Boulevard and 90's Boulevard. They're basically two cities full of massive posters/statues/references of many Sega games and consoles from the aforementioned decades.
Anyways, I was playing through the 90's Boulevard when lo and behold, there it was: a fairly big Shenmue poster on the side of a building towards the end of the circuit (box art of the original game).
Apologies if this has already been mentioned, and I know it's nothing special, but it is the first official Shenmue reference in a Sega game for many, many years, is it not? (The Virtua Fighter 5 tags were fan-made, I believe.)
Nice to see that SEGA aren't completely denying the series' existence...