Quoted from lukerp:

1) TAF - yes, it's an A-list machine, no, it's not cheap, but EVERYONE remembers that game and I think it would do well because of it
2) T2 - cheap; anyone old enough to remember the movie coming out will throw money at it
3) South Park - relatively cheap; people will throw money at it based on theme alone. This was not my idea; I probably wouldn't have thought of it had those above not said anything, but for a quarter-taker, it'll definitely do the job.
4, 5, and 6) Space Shuttle, High Speed, Pin*Bot - there's something to be said for relatively simple games that revitalized the pinball industry. These hit the cross section of being relatively cheap and somewhat appealing to dedicated pin players.
7) RFM / SWE1 - I wouldn't write those in stone; they're cheap enough, but also have the advantage of being novel for non-pinheads. Would I put one in my basement? Probably not. Did I think, "Holy crap! This is really cool!" the one and only time I played RFM? Yes.
DE Simpsons. I have a TSPP and love it, but for a third of the price, the other one will take quarters just fine.
9) Fish Tales - Same reason as Space Shuttle / High Speed / Pin*Bot, a bit more money, but a player's game that will also draw money from the person passing through because the topper's cool
10) Hyperball - I'm going out on a limb here, but I think a lot of people would throw a quarter or two in this thing for the sheer novelty value of it, pinball fan or not. As I understand it, this is TREMENDOUSLY loud, which is part of the appeal, but keep that in mind and put it at the back of the room...
11) Earthshaker - looks cool; game with a shaker motor catches people off guard when it fires up
12) World Cup Soccer - relatively inexpensive; again, cross section of price and appealing to pinball players
I can't think of any others with good reason, but since I've made this list with some quasi-reason behind it, I'll say:
13) Flash
14) Gorgar
Why those two? I like 'em, that's why. No other "they're great bang-for-the-buck" logic therein.
I'd be REALLY interested to hear an operator say, "Well, Luke, your list looks good from a money-making standpoint," or, "Luke, have you been huffing paint thinner again? None of those games made money the first time around." Good luck on this endeavor.
Luke