Really depends on what your startup is and what stage you're at.
As Eric mentioned, for early stage, the team is always super important. If it's a strength for you business, put it up front. If it's not your strongest point, move it to the back. When I'm talking strength, I really mean that an investor will look at the team slide alone and think "wow, I'd invest in almost anything these guys did".
Otherwise, the most important slide(s) vary. For example:
- In something like a marketplace, the market size and problem solved is critical at an early stage. For a later stage, traction numbers are most important.
- In a medical device company, the solution is very important (along with the team of course).
-In a Saas business, perhaps it's go-to-market strategy and business model.
But as a rule of thumb, for early stage companies, think team and market size (TAM usually). For later stage, think traction and business model.