Russia's effort to develop an F-22 class fighter (the PAK FA) is going to require a lot of work. The prototype, that took its first flight recently, was clearly the basic Su-27 airframe modified to be stealthier. This included changing the shape of the aircraft to be less radar reflective, and providing internal bays for bombs and missiles. But there's much more to do in order to achieve anything close to the stealthiness of the F-22. It took fifteen years for the F-22 to go from initial flight, to entering service. The PAK FA could proceed faster, learning from the F-22 experience (especially if some of the Internet based espionage carried out in the last decade was Russian). But such development speed has not been a Russian characteristic.
Another problem is the engines, which were not ready for the first flight. Older model engines were used, because initial flights are mainly to confirm the basic airworthiness of the airframe. The new engines, also being used in the Su-35, are suffering development problems. The Russians have always had difficulties with their high end military engines, and that tradition continues. Currently, the Russians say it will take several years to perfect the new engine.
Russia will also need a new family of air-to-air missiles, as the current ones are too large for the internal bays on the PAK FA prototype. These are already in the works, along with more compact versions of air-to-surface missiles. There are also problems with the electronics and, well, you get the picture.