In-game and out, the scope was so much smaller and the plot much more affecting for it.
It's ironic-the first game was all about petty politicking and squabbles between the Zerg, Protoss, and Terrans over limited resources. The deluge of hard-to-parse proper nouns and space magic is enough to douse even the tiniest spark of interest at this point. If you haven't paid attention to the lore of StarCraft II up to this point, now is a terrible time to start. Only Artanis, Hierarch of the Protoss, can save the Koprulu Sector by uniting the Daelaam, Tal'darim, and Nerazim against him. A rogue Xel'Naga, Amon, looks to slaughter the Firstborn and end the cycle of life and death.