As the author of the Lonely Planet guide so eloquently puts it; "Komsomolsk isn't Russian for 'spirited dining scene'"...
Golden Buddha Cafe
Aside from a selection of Chinese cuisine, this place offers excellent Green Tea, and more importantly a wide variety of cocktails and other alchohol. Sometimes have live music, though it's mainly "restaurant style" table seating, so best for groups.
Heilongjiang Restaurant
Popular Chinese option, which also serves a bit of Russian cuisine. Live music in the evenings from 21 Tu-Su. Unlike to stir much excitement, but it's not bad either if you avoid the deep-friend-greasy stuff.
Suin Restaurant
Interesting, if upscale and slightly expensive option, as they besides some usual suspects from the Russian and European kitchens, had a few traditional Nanai dishes on the menu at the latest visit.
Sushi City
For a frontier restaurant rather fancy and modern decór, obviously sells Sushi and other usual suspects of the Japanese kitchen. Also has take-away which is a nice concept for the train journey don't you think? though, if you're a regular at high-class sushi joint's back home, you might want to give it a miss.