Lottery system is dead, indeed. You should try changing it as Karthik suggested so we could see if players will be more or less interested in it than they're now.
There should be jackpot round of 1 million every 15 minutes (unlike current 30 minutes which is annoying and boring) that consists of 7 numbers and If we wanted to participate in jackpot, we should pay entry fee (buy a ticket) of 100k. After we buy it, we could choose ten numbers from 1-100. If we guess 7 of them, we get 100% (1,1m in this case - if I'm the only one that bought the ticket). If we guess 5 or 6, we get 75%, if 3 or 4 - 50% and if 2 or 3, our money spent on ticket just gets returned..
Does it sound too difficult maybe? It's pretty similar to what you've suggested.