I'd rather have Markakis and Lincecum then Sizemore and Rios. I personally think Rios is amongst the most overrated fantasy players, and Markakis amongst the most underrated. I think you have speed to burn, and can afford to move Sizemore. Markakis is likely to post a higher batting average with a handful fewer HR's (though I could see this being the season his power really takes off) and the big difference between Sizemore and Markakis coming in their SB totals. Markakis is likely to post 10+ SB's and could post as many as 20 SB's. So he will certainly contribute something to the SB department.
Breaking down the rest of the deal I don't even think it's close. I'd take Lincecum 10 times out of 10 over Rios. Lincecum is without question amongst the top 5 SP's in fantasy, and arguably the top fantasy pitcher after last year's performance. Pairing him with another top 5 SP gives you what I'd imagine has to be the best 1-2 in your league. I'd do this deal and not think twice about it.
I hope that is of some assistance. I need a little help myself, and if you don't mind I'd like your two cents on a question of my own. viewtopic.php?t=364919