@williamcaput said in Megadrive ROM language select:
RetroPie Version Used (eg 3.6, 3.8.1, 4.1 - do not write latest): 4.6.1
The 4.6.0 series had EmulationStation at version 2.9.1, your log shows an much older version (2.6.1) is in use. Are you sure you're using RetroPie 4.6.1 ?
The log shows the ROM files are launched fine. I would check the ROM files as @windg suggested and maybe post a verbose log from launching with lr-picodrive. Use pastebin.com for the output, since they're quite large.