Well you ruled out Mrs. Knott's Chicken Dinner Restaurant which is pretty good. If you hit it during the right time of the day there shouldn't be a line. Knott's has plenty of places to eat, all about the same to me as far as "taste wise" goes. Maybe someone that has been there more recently than I can help shed some light for you.
Sutter's Fine Family Fare: Burgers, pizza, hot dogs, funnel cakes.
Grizzly Creek Lodge (Formerly Lucy's Lunchbox): Burgers, sandwiches, salads.
Pancho's Tacos: Tacos, nachos, burritos, tortas.
La Victoria Cantina: Fajitas, burritos, tacos, churro twists.
Papa Loca: Chili fries, carne asada fries, bleu cheese fries.
Johnny Rockets: Burgers, fries, shakes.
Hollywood Hits: Pizza.
Coaster Diner: Burgers, fries, shakes.
I am going to be completely honest with you. No food inside the park is that great. If you really want to eat in the park, I would go with the Fireman's Brigade (get the BBQ corn, too!) or Papa Loca and grub on some carne fries. The Calico Saloon over at Ghost Town is also good if you want a Sasparilla or something different to drink. You can't not get a funnel cake while you're there either.
The only food in the park that is "brand name" that I've found is ok is Panda Express. Everything else (Johnny Rockets, TGI Friday's, Pinks) is pretty below par. But there you go! Best of luck to you!
Coaster's used to be okay, but the last couple of times we've been up there we were greatly disappointed. They had changed the type of french fries that they were serving from the traditional crinkle cut to the uber large steak fries, which neither my wife and I care for.
The Chicken Dinner Restaurant's iconic chicken dinner is outstanding, but for in-park dining I'd go to the Ghost Town Grille. Their meatloaf entree is incredible and comes with fresh green beans, corn on the cob, and mashed potatoes. The chili is excellent too and I now order their fresh-brewed iced tea which his far better than the fountain tea they'd been serving.
Over in Fiesta Village, they've got a little taco stand that I like too. Forget about the chain restaurants, Panda and Johnny's. You can eat that reheated stuff anywhere. Go to the Ghost Town Grille instead!
The Chicken Dinner restaurant does usually have a line, but it also typically moves pretty fast, much faster than the typical restaurant. There's a lot of tables in there, so there's generally one turning over every few minutes. So don't let a long line there necessarily dissuade you.
Aside from that, I do concur with Ghost Town Grille. Although I haven't had a chance to try the new menu, I liked it before, and people seem to like it even better now.
If you're willing to head outside the park, TGI Friday's is there (and they do give a discount to Knott's APs), and a short drive away is Tokyo Time, Claim Jumper, Philly's Best Cheesesteaks, and Pat & Oscar's may still be around.
Well, according to their website (and granted, that could be out of date), the only Pat and Oscar's left is in Temecula. Even assuming that is open, it's nowhere near Knott's.
But mine,mine,mine is right... they have mostly changed to O's American Kitchen (and what a terrible name for a restaurant chain), and the menu does seem similar, including the all important breadsticks.
I do say "mostly", because the Pat and Oscar's that used to be off Los Feliz Blvd has changed to a Souplantation. So not all became O's American Kitchen.
Other than the Chicken store, that always has a long line.
This statement implies that you might know of the quality of the food but are only deterred by the long line.
1) Mrs. Knotts' chicken is really the best place to eat. Don't write it off just because of the line.
2) the quickest way around the line is to NOT eat in he sit-down restaurant but rather order from the take-out counter next to it. ( Just down the sidewalk about 20 feet south of the restaurant entrance doors. )