This guide is for PS2. First, make sure difficulty is on Easy. (Options > Difficulty > Easy)

Then head to Story Mode. Pick New Game and choose Kiryu. (This run consists mostly of abusing Kiryu's Punch Attack, Fierce Attack, Beam Attack and Forward+O.)

I am fairly uneducated on the PS2 version, but have tested out a few monsters myself, the GDF story ends relatively short and Kiryu gives good damage when multi-punching, as well as the movement from Forward+O is really useful.

On the PS2 version, Surge Attacks seem to be almost worthless, so for every stage that includes a Power Surge, break the powersurge crystals instead of attacking the monsters.

Time starts on selection of first level.

Day 1 - Osaka 1 - Basic Training: Pick Osaka and head straight, use Punch Attack, Fierce Attack, Beam Attack, Special Attack to kill Anguirus.

Day 2 - San Francisco - Taste Of Power: Pick San Francisco and destroy all the powersurge crystals. (Use Forward+O for movement.)

Day 3 - Sydney 1 - Frozen Terror: Pick Sydney and use Punch Attack to destroy all the Crystal Towers. (Use Forward+O for movement.)

Day 4 - Osaka 2 - Gassed: Pick Osaka and destroy all the powersurge crystals. (Use Forward+O for movement.)

Day 5 - Tokyo - Rumble in the Surf: Pick Tokyo and destroy all the powersurge crystals. (Use Forward+O for movement.)

Day 6 - New York 1 - Terran Mind-Control: Pick Osaka and destroy all the powersurge crystals. (Use Forward+O for movement.)

Day 7 - Seattle 1 - Trouble Brewing: Pick Seattle and destroy all the powersurge crystals. (Use Forward+O for movement.)

Day 8 - Sydney 2 - Soloist: Pick Sydney and destroy all the powersurge crystals. (Use Forward+O for movement.)

Day 9 - Osaka 3 - Easy Prey: Pick Osaka and head straight, use Punch Attack, Fierce Attack, Beam Attack to kill Orga.

Day 10 - Monster Island - Power Overwhelming: Pick Monster Island and destroy all the powersurge crystals. (Use Forward+O for movement.)

Day 11 - Seattle 2 - Big Trouble: Pick Seattle and head straight, use Punch Attack, Fierce Attack, Beam Attack to kill King Ghidorah.

Day 12 - Sydney 3 - Ganging Up: Pick Sydney and head straight, use Punch Attack, Fierce Attack, Beam Attack to kill Megaguirus and Obsidius. (Injuring Megaguirus and letting Obsidius kill Megaguirus works but seems to be RNG.)

Day 13 - New York 2 - The Siege: Pick New York and head straight, use Punch Attack, Fierce Attack, Beam Attack to kill Battra. (Killing only Megaguirus works but seems to be RNG.)

Day 14 - New York 3 - Finale: Pick New York and head straight, use Punch Attack, Fierce Attack, Beam Attack to kill SpaceGodzilla.

Time ends on the final hit on SpaceGodzilla in the final level.