Is the Wii a DVD Player?

Technically yes, but practically no.

• Can play DVD-Video: With homebrew (Homebrew Channel → DVDX / MPlayer CE) or early system menu hacks.
• Not a dedicated player: No remote, no chapter skip, no region-free, no upscaling, no Blu-ray.
• Laser wear: Movie playback stresses the drive more than games.

Verdict: It's a game console with a DVD drive. Use a $20 dedicated DVD/Blu-ray player instead.