Bitcoin blocks will always be ~10 minutes, if you pay the fee to get into the next block, it'll be 10 minutes until your payment is confirmed, before that, all the nodes will announce it anyway so 0 conf is much faster.
On top of that, if you want to pay less than a certain transaction fee (right now it's $1.62) you probably won't get into the next block, see https://bitcoinfees.github.io. Recall that 1 block = 20 minutes and add that on top of the confirmation time.
 https://blockchain.info/block/0000000000000000005f0e639f66af... look at the Timestamps of this block and the Previous Block
 https://bitcoin.org/bitcoin.pdf page 8
 https://bitcoinfees.21.co/ (a satoshi is 0.00000001 BTC, 10,000 satoshi is 40 cents right now)
Users don't want to play a complicated expensive, impossible to win game in order to get their payments processed in a known timeframe.