I'd say the F-15E is pretty unproven in the anti-shipping role as well... I guess you are asking two questions.
Regarding the naval strike, they are pretty much unproven because the proposed upgrades for the Su-33 (Su-33M/MK) and Su-34 (Su-32FN) didn't get any orders. The multi-role Flankers are capable of AShM but most operators don't use it for this role. The only exception is China, which has the Su-30MKK2 on order for the PLANAF, it is a derivative of the KnAAPO-built Su-30MKK optimized for the maritime attack role. So I'd watch the news on China/Russia exercises involving the Navies. China was also interesting in the Su-33, so I guess they will be upgraded.
The Russians might be upgrading the Su-33 fleet once the new carriers are ready, but until then I am pretty sure the ASh role is left to the Su-24M, Tu-22M, and the fleet / coastal defences.
Regarding the strike role, the multi-role Flankers have not proven themself yet outside the test-range. Again, I'd say that this is because they are not mature in the A-S role yet. If you look at export customers, they first and foremost need a new fighter for air defense. The aircraft are not even fitted with the full A-S suite yet (same for the Rafale/Typhoon by the way, and haven't seen a Gripen prove itself in the A-to-S role either). Also the first Su-30MK demonstrator came about in 1993, the F-15E had already had the opportunity to prove itself in the Gulf in 1991. If you look at all the conflicts since then, I'm pretty sure the Flanker will never catch up with that anymore (and that is a good thing... peace).
I'd watch the Su-34, in production right now. It already set various payload/distance records for its class, beating the F-15E.
The only problem I have, is that IMHO Western ASMs, AShMs and PGMs are way better than the Russian equivalents.