The Sukhoi "Flanker" airframe (ie. airframe development project no. Sukhoi-T10-1 through 15, for example), is released in the various Flanker and Platypus models which include the 27, 30, 33, 34, 35 and 37 aircraft portfolios and their variants. They're all Su-27s in UB, K, IB and PU portfolio designations, among others.
So which Sukhoi "Su-27" are you talking about? The latest SuperFlankers are more than capable of going toe to toe with an F-22 and are likely to outmatch all other aircraft currently in service. The 1981 model clearly outmatches any fighters which were in service during that decade...or the next.
The basic airframe development itself was named for the first combat portfolio delivery which was earmarked, the Su-27 basic fighter to be offered for export.
The 15 T-10 prototypes were therefore named the Su-27 and they promptly started killing pilots. The "Flanker-A" never saw service for this reason.
A "Flanker-B" was developed through redesign and that became the Su-27. But that's not the one people saw in air shows like Farnborough.
A special P-42 development was used to test the airframe limitations and this is the one which set the 27 world records currently held by the Flanker airframe, including rate of climb to 40,000-odd feet in just over 55.5 seconds.
The Su-27PU (Su-30) is a specialised, two seat long range interceptor designed to slave rig up to four single seat Su-27 "Flanker-B" variants into its avionics via radio data link so they can switch off their radars and still target enemy aircraft with complete electronic invisibility. It's basically a redesigned Su-27UB orientated for 10+hr individual missions, the new generation AWACS you don't want to mess with as it's still fully combat capable and usually very heavily armed.
The Su-27IB and KU Flankers (Su-34 "Platypus") are a side by side two seat configuration that can deliver a deep penetration strike package on missions so long it has a galley in the cabin and retains the fighter performance of a front line interceptor for self defence. It's a 21st century F-111 and easily outclasses the deep penetration strike capabilities of the F-22A
and its proposed derivatives (FB-22 delta wing tactical strike aircraft).
The F-22 has a released top speed of Mach 1.8 by the way, rated closer to Mach 2 by independant enthusiasts, and is designed for high load bearing, low-mid altitude performance (helped with 2D variable geometry engine outlets) and multirole capability (a feature built in to its ubiquitous avionics, it needs only a software tape to perform penetration strike roles, for example). Its main feature is supercruise, that is non-augumentation supersonic flight for increased range under combat conditions, and a high survivability (low radar visibility and EM emission).
Its air superiority feature was never designed to be a focus, but a capability. It is an excellent aircraft, but is ridiculously expensive and thus was fully intended to unify as many requirements as possible, including parts commonality with other new generation US aircraft.
The Su-35 Flanker ("SuperFlanker") has a rearward facing radar for over the shoulder missile fire (just like the movie "Firefox"), a triplane canard layout, higher rated engines (some 29,900lbs st aug. apiece), and a new avionics package. This is the basic air superiority variant and is easily en par with the most advanced fighters in the world.
When tacticians say the Eurofighter can take on a Flanker, they're most certainly not talking about this one. Introduced as a stop-gap for the Su-37 whilst its engines were under development.
Su-37 SuperFlanker has engines rated for Mach 3 (airframe design limits are still Mach 2.35), 3D variable geometry exhaust outlets and updated avionics again. It was probably conceived to counter the YF-22A, which it is likely to do, since such things were not in the engineering requirements of the YF-22 in the first place, the previous two decades of typical US military action was.
As the eventuation of a design concept begun in 1969, the SuperFlanker is probably the last true remnant of the Cold War era. It's deadly.
Su-47 Berkut is a different airframe, with forward swept wings, stealth features and 3D variable geometry outlets. Emphasis appears to have moved to high transonic performance against older and export aircraft as opposed to single purpose fighter-interceptors that can also lay waste to a small city.
As is typical of all the latest fighters of the 21st century, the SuperFlankers and Berkut series avionics can probably tell you how much an enemy pilot weighs, what he was thinking about last night and does better CGI than George Lucas. The thought that Flankers have poor avionics is ridiculous (this was a reputation given to early and export MiG-29S and SE Fulcrums which were not fly-by-wire, the latter as is typical of Soviet exports also had downgraded radar; resolved in the MiG-29M indigenous to CIS air forces).
The Flanker is probably one of the projects which broke the Soviet economy, now the basic Su-27 Flanker-B and Su-27UB variants are available dirt cheap on the export market, along with the excellent MiG-29 Fulcrum (the detuned version as far as I know). It's less expensive and a much better prospect than equipping with used Eagles and export Vipers for a small nation, hence has been growing in popularity in the Asiatic region. The only decent thing about these yesteryear fighter exports from the US is the product support, which although ridiculously expensive (bit of a theme for the US military expenditure really, isn't it), at least it exists.
Here's a picture of an Su-37 SuperFlanker. Pray they never deliver them to the Middle East.
Here's a Platypus variant.
Here's the Berkut.