Really? Same Major version numbers. Same product family name (SQL/Hyper-V 2008). If your databases and virtual machines don't use any new features you might expect that they could be moved between servers. Or at least have the option to save a backup in a "compatible" format.

I think it's mostly my thing getting stuck on the naming of it, for me just slapping an "R2" on the 2008 line of server products (Windows, Hyper-V, SQL) instead of being consistent with their other year-based product names makes it seem like they are minor updates instead of different products.