Good battery for cold temp start?

Hi guys, just purchased a L sedan and I am thinking about switching out the battery. Although the precious owner said its new, its been sitting in his garage for 2 and a half years. Right after i drove it home and let it sit for like 2 days, the battery died and had to get jump started (i forgot to turn the headlight off but isnt 2 days way too fast?) Whenever i start my car in the morning it takes like 4-6 cranks to start the engine (buffalo winter).