Arduino Code - simple if, else statement?

This line:

if (digitalRead(led1 == HIGH))

Is incorrect. This should be:

if (digitalRead(led1) == HIGH)

Because you want to check the return value of digitalRead(). However, this doesn't cause the problem.

You can see the real problem when you try to think as the microcontroller. It does these steps (I start at digitalWrite(led1, HIGH)):

1. Set LED1 high
2. Wait
3. Set LED1 low
4. Wait
5. Check:
   1. If LED1 is high, set LED2 high
   2. If LED1 is low, set LED2 low
6. Go to 1.

When 5 is executed, the value of LED1 is always low. 5.2 will always be executed, 5.1 never. If you want to achieve this programmatically, you could use something like this:

void loop() {
    digitalWrite(led1, HIGH);
    digitalWrite(led2, HIGH);
    delay(5000);
    digitalWrite(led1, LOW);
    digitalWrite(led2, LOW);
    delay(3000);
}

If you want to do this with an if, you can either do something like this:

void calcLed2() {
    if (digitalRead(led1) == HIGH) {
        digitalWrite(led2, HIGH);
    } else {
        digitalWrite(led2, LOW);
    }
}

void loop() {
    digitalWrite(led1, HIGH);
    calcLed2();
    delay(5000);
    digitalWrite(led1, LOW);
    delay(3000);
}

Or put the if loop in the loop() (i.e. without a function call).

It would also be good practice if you set the initial state of the machine in your setup(). For example, set both LEDs high or both LEDs low. If you don't do this, it will work, but might give unexpected results in the first few seconds.

your if statement is incorrect, what you want is

if (digitalRead(led1) == HIGH)
{
    digitalWrite(led2, HIGH);
}
else
{
    digitalWrite(led2, LOW); //This line won't work.
} 

However, as Camil has already pointed out, there are other issues as well.

Your original "if" statement would get evaluated as follows: First, the "led1 == HIGH" statement gets evaluated. Since you defined led1 as 2, and "HIGH" is (presumably) defined as 1, this should result in a boolean FALSE, or the value 0. This result (the value 0) is then passed as input to the digitalRead function. Since this function expects an Arduino pin number as input, it effectively tries to read the value of pin 0 (which I don't think is defined). This nonetheless appears to results in a value greater than one, so that the body of the if clause is executed as your LED2 is evidently turned on.

As Camil already pointed out, with only the change in the if statement, your LED2 would never actually turn on, since at the end of the loop(), LED1 would always be off/low. So if all you want to do is turn on or off several pins, you could just use two digitalWrite() calls. If you do need to check if one pin is low or high (e.g. because other parts of the code can change its state), then you do need to make sure to do the comparison the against the output of digitalRead(), an not within its input.