I don't think that Congo should automatically make you opt to not get Tron. With few exceptions, even if layouts are very similar, they still play totally different. You can only arrange a playfield so many different ways...

As for the few that I think are extremely similar...

Striker Xtreme *is* NFL.
Family Guy *is* Shrek.
Pinbot *is* Jackbot.
Austin Powers *is almost* Iron Man. (Or, is Iron Man LE as I often joke.)
LOTR *is almost* Sopranos, and even that might not be close enough to bug me - but I don't like LOTR, so I don't have to worry about that.

Beyond those five, I had Whirlwind and JP next to each other for a while without issue. Very similar layouts, gameplay so different that it doesn't bother me at all.

Except Shrek and Family Guy.

Also, I forgot NBA and Space Jam as being incredibly similar.

They based the layout of NBA on the layout of Space Jam, but then cut some of the costly wireforms and whatnot out of it and added a VUK-ish type shot that fires the ball across the playfield into the hoop that is really visually stunning.

NBA is a great game in my opinion, even though it appears to be the 'cut down' version of the game. Space Jam I don't like at all. Regardless, considering the ramps and about 3/4ths of the playfield are exactly identical, I wouldn't think you would want both in the same collection.

When you put them beside each other like that, it always surprises me just how different TAF and JP actually are. They both have a divertable ramp and three flippers in about the same spots, but beyond that, uh...