I spent a couple months in phnom penh this year. here is my take on the restaurant scene there. almost everything is within ten minutes by taxi (though there aren't many) or tut tut which are oversupplied.
French: plenty of french. Best is 112 (was called 102, recently renamed or renumbered after the talented original chef was killed in a car accident) located on street 102 in colonial mansion. elegant colonial decoration. everything good. liked the pan fried fois gras, salads especially the nicoise, lobster bisque, terrific onion soup, steaks, osso bucco, real good desserts. Vans is nearby. similarly decorated in a colonial building. also good. Topaz on Norodom is beautifully decorated in modern style. very good appetizers. main courses not quite up to the competition. they should change their beef supplier. 112, Vans, and topaz are fairly expensive, though not crazy. two good and more reasonable places: atmosphere on norodom just south of the independence monument is pleasant. good basic french entrees: onglet, beef bourgignon, coq au vin. appetizers not so imaginative. best dessert is the flan. comme a la maison is a bakery as well as a restaurant. everything pretty good. only downside in hot phnom penh: no AC. bouganvillier on the river front i don't recommend. okay food, bad service, expensive.
my favorite restaurant is Pacharan on the riverfront. Spanish with very good tapas. terrific Jamon Iberico, patata bravas, salad with lentils, very good specials. i was never dissappointed. the only italian i tried was luna d'autonno. as the chinese say, the chef must be in love. everything tastes sweet to him resulting in unfortunate oversalting. friends say the pizza is good but i never tried it. Tell is a well-run, comfortable german restaurant. i liked the sausages and the beer. le cedre on street 360 a couple houses west of norodom good lebanese cooking. it looks like they are going to open a second place on the river.
bar food: Freebird on street 240 good food and pleasant staff. classic american rock and roll bar decoration. FCC (Foreign correspondents club) on the river. good view from fourth floor roof bar. okay food. nice place. also recommended on the river front: le quay (crepes), metro, and chow. all new, good looking joints with interesting food. avoid steve's steakhouse unless you care for boiled steak.
asian: coca by the intercontinetal (with raffles the best hotels in PP) good for chinese/thai. golden cattle seafood chinese hot pot also good. man han lou for good chinese with a microbrewery. the guinness clone was admirable. they also do an emerald green lager (seaweed) that i liked. next door is master kang, a seriously good massage place. chinese, thai, and reflexology. men and women clientele, about 20-25 masseuses (most from china) on duty. amrita spa (more of a spa with good thai massage too) on the riverfront also recommended.
for korean either le seoul (better food) or pyongyang (better show). pyongyang is a north korean government run restaurant. the food is decent (korean ain't my favorite so i am probably no judge) but the show is cool. the waitresses are NK military and they sing and dance korean favorites. the place is usually packed with korean tourists and business people. there's a lot of korean investment in cambodia. the real estate bubble there is korean made.
malis: cambodian fusion. pretty interesting. nice decorartion. comfortable. run by the same thai family that owns topaz. cambodian food needs some help and this place provides it.
pho 24: vietnamese chain. pretty good noodles.
shiva shakti on sihanouk east of the independence monument. good indian. butter chicken really good.
yamato: japanese like benihanas. okay. fusion sushi in the hotel cara was good and the nicely decorated hotel is a total bargain at $40 a night.
if you get to sihanoukville (a four hour drive over a good two lane highway) i can recommend le vivier de la paillote.