Is Mortal Kombat vs. DC Universe on Wii?

No. Mortal Kombat vs. DC Universe (2008) released only on:

• PlayStation 3
• Xbox 360
• PlayStation Portable (PSP) — Mortal Kombat: Unchained (port with extra chars)

The Wii did not receive a port. Reasons cited: hardware limitations (CPU/GPU/RAM), storage (DVD vs. Wii disc), and Midway's financial state.

Mortal Kombat on Wii

• Mortal Kombat: Armageddon (2007) — Wii version has motion controls, Kreate-a-Fighter, Khameleon exclusive.
• Mortal Kombat 1 (2023) — Not on Wii (Switch/PS5/Xbox/PC).

If you want MK vs. DC on Nintendo hardware, only option is PSP via PPSSPP emulator on Wii U (vWii) or Switch (homebrew) — not native.