Get overpowered hardware to cope with running the software.
Repeat the dolphin setting optimization for that build.
Try another fork or unstable build of dolphin.
Game Config: Speed up disc transfer rate.
If using DSP, use this guide to dump DSP files with a Homebrew-enabled Wii (if you have a Wii, that is).
DSP Emulator engine to DSP HLE Emulation (fast, but you may encounter audio glitches, if so, you may want to switch to DSP LLE Recompiler which is slower but more accurate).
Reduce detail in your graphics card settings to improve performance.
Fast Depth Calculation (may cause flickering textures, try on and off).
OpenMP Texture Decoder (in rare instances it can "max out all cores" and hurt more than it helps).
Disable Destination Alpha (may crash, try and on and off).
Cache Display List (may crash, try and on and off).
Set CPU Emulator Engine to JIT or JITL (if latter may has issues, use JIT.
Rightclick Game Window -> Properties -> Alternate Wiimote Timing.
Internal Resolution: 1x Native (640x528).
graphics options: Advanced tab: all checkboxes.
The latest stable build of Dolphin (64-bit if you have a 64-bit machine) Arguably Sunshine is the favorite of the series. The main fork of Dolphin isn't optimized for running Super Mario Galaxy 2. Super Mario Sunshine (USA) is the gamecube adventure title for Mario, With a distinctive graphical enhancement from older outings and an outstanding assortment of intelligent gameplay, Sunshine is a winning combination shined well to end up with a fantastic polish.