Mercenaries 2
I'm currently having a lot more fun with Mercs 2 then I ever had with GTA4. Proves that blowing up shit is a lot more important then story in sandbox games. At least to me he. The game is a bit rough around the edges and has a number of minor bugs and glitches, but all the important stuff (controls, gun feedback, immersion, frequency of oh-shit moments) is much better then in GTA (IMHO of course). Battling a group of 3 or 4 heavy tanks in an army-occupied city only with RPGs and C4 is an absolutely exhausting experience, but so much fun with buildings crumbling left and right, tank shells and RPGs whizzing by and the distinctive sound of distant sniper fire over the general combat noise. Of course the player could opt to level the entire city with a few air strikes, but that would cost a lot of civilian lifes and wouldn't be well received by the Guerilla. And besides, air strikes are freaking expensive ;)