9. Space Harrier & Hang-On (Shenmue)
The inclusion of fully-playable versions of Space Harrier and Hang-On within Shenmue and its sequel served a specific purpose, demonstrating that the Dreamcast's opus offered an unrivalled level of immersion. Anything that wasn't bolted down could be picked up and almost every object in the world could be manipulated.
Much to the delight of the retro heads, this included the coin-op cabinets at the in-game arcade, which happened to include the aforementioned Mega Drive hits, siiting proudly beside other Sega classics like Virtua Fighter.
Shenmue tasked players with avenging their father's murder, but many of them were too sidetracked by cracking Easter eggs like this one to make significant progress with the main story quest. Everything in the world was out to distract you.
Space Harrier and Hang-On's inclusion in Shenmue is down to more than just Sega publishing all three games. Yu Suzuki created each of these series and is now hard at work on a third Shenmue title, which will hopefully include more playable retro games.