Are you allowed to attack creatures instead of a player during the combat phase? Because it seems to me it's much more easier to block (because you can actually choose what you attack) than to just throw all your critters at the player and hope the right ones don't get blocked.
Since this is a basic rules question, a quote from the basic rules:
In your combat phase, you choose which of your creatures will attack, and you choose who or what they will attack. Each one can attack your opponent or one of your opponent’s planeswalkers, but not any of his or her creatures.
You say it'd be easier to just attack creatures. Sure - and that's kind of the point. If you could just use a bigger creature to kill off a smaller creature, combat wouldn't be nearly so interesting, and the game would lose a lot. You really do have to work out how to manage to attack your opponent and get through without losing too many creatures or leaving yourself vulnerable. It's more work, but it's part of what makes the game interesting and challenging, and gives you an edge if you're better at it than your opponent.
No, you cannot. You can only attack a player, or a planeswalker he or she controls.
508.1. First, the active player declares attackers. This turn-based action doesn't use the stack. To declare attackers, the active player follows the steps below, in order. If at any point during the declaration of attackers, the active player is unable to comply with any of the steps listed below, the declaration is illegal; the game returns to the moment before the declaration (see rule 717, "Handling Illegal Actions").
508.1a The active player chooses which creatures that he or she controls, if any, will attack. The chosen creatures must be untapped, and each one must either have haste or have been controlled by the active player continuously since the turn began.
508.1b If the defending player controls any planeswalkers, or the game allows the active player to attack multiple other players, the active player announces which player or planeswalker each of the chosen creatures is attacking.