I don't think it's a case of limited scope mentality or even of game quality. I've had around 8-10 of the top DE and Sega games cycle through my collection and they are just as reliable and nearly as solid feeling as my WPC games. I think the area where DE was lacking compared to the top WPC games was in the ingenuity and the talent level of the people designing and programming the games. Guys like Kaminkow, Borg and Seckel were/are pretty good designers but honestly I think guys like Pat Lawlor, Steve Ritchie, and Brian Eddy were much more creative in their games. Many of the DE designs were copied or heavily influenced by WPC games. JP is heavily copied from Whirlwind, Tommy is copied from Funhouse, Batman Forever is heavily influenced by STTNG, etc. Also, a lot of the DE software leaves something to be desired.-the gimme multiball on ball 3 for instance and the repetitive audio and sound quotes. My favorite DE games is Tommy and I think a big reason for that is because Lyman Sheets did the software.
I like games like JP, but to compare it to a mechanical masterpiece like TZ or TAF is doing Pat Lawlor a disservice.-especially since it's basically a copy of one of his designs. I think if DE had the design/sound/art/programming staff that Williams/Bally had in the 90's that they would have the most collectible games today. It's not just about the company making the games, it's about the heart and soul of the people that worked there.