May I know if GREAT WEALTH Multiplier 15 is a good plan as compared to other similar one?

Great wealth Multiplier is a perpetual endowment plan. So basically it a type of endowment plan that last for the lifetime of the life assured. Usually can also appoint a second life assured, but the maturity will still be based one the 1st policyholder.

For the sum assured in proposed in your case, it would mean that you will have to pay premium of 50k (either in 5, 10, 15, 20 years). So you may pay as low as $2.5k per annum.
It take usually about 15 years before it could even break even. (Something for you to think about, cause 15 years is a long time and your perspective on life could change)

Honestly for me, I will think it a decent plan for someone who is very risk adverse and dont need the money for a very long time (30years at least, 15years to break even, 30years to make any meaningful return). This type of plan can act as a 'safety net' for your financial portfolio.

I will think it better if you consult an independent financial advisor who can help you compare other perpetual plans, just to make sure you don't lose out.