We are not all equal in this game. If you live in north America, the credit card game is more than substantial. But in the rest of the world, you cannot count on it saldy.
The mileage game has gone tougher over the years. Earning has moved from the distance you were flying...to a revenue base earning. It simply means that if you fly on the cheapest ticket, you will receive close to no miles. And if you do want 100% miles earning, the price of the ticket is often ridiculous. So it's all a trade to deal with!
Miles per se are not that of a good deal, what is the good is to get the status with an airline or an alliance. Gold, will give you access to business class queue....but more important (except on domestic flights in North America), it will give you access to lounges...that means food, drinks, shower...a place of civility to wait for your next flight.
Upgrades, those we all dream at the gate when a flight is full...will only happen if you have one of this elite status...It's roughly....those who fly the insane way...150,000 miles per year...Platinum....today, the equivalent of 21 returns London-New york per year....in a high paying economy seat!
The decent level is 50000 miles to get to Gold. I will do for example few hours more in a plane today, for the same price as a direct flight...just to get those 50k....may sound crazy, but not when you fly in the back of the plane...lounges, no queues, exit row and upgrade makes flying a little more fun from time to time!
Silver will be yours for around 25,000 miles....that can be as low as 2 return per year from Europe to Asia. You may have access to some lounge...some more civility...but you are always at the end of the upgrade queue...
The truth these days is that the same game apply to hotels....and that can be a much more beneficial game...starwood, once you've done 25 stays per year, will upgrade you, from a basic room to 80% (outside of North America) to a suite. If there is a lounge, this is a free breakfast...and in Asia, it's a free decent buffet between 5.30pm and 7.30pm with all the drinks you want. Suddenly, a 5 stars hotel for less than 100usd in Kuala Lumpur can become cheaper than a basic hotel.