Recreate "Voltage gain vs Frequency" graph of Op-Amp in LT Spice
Well - here is the explanation for the unexpected behaviour.

You are not simulating open-loop but with feedback. I suppose that you are aware of this. For open-loop simulation you must take some actions to ensure a correct bias point within the linear amplification range

More interesting: What happens when the frequency is increasing up to pretty large values? The gain of the opamp decreases and with it the loop gain of the whole circuit. More than that, the inverting input node cannot longer be regarded as &quot;virtual ground&quot;. And now the output resistance r_out of the opamp comes into the play. Due to the loop gain drop the output resistance is increasing and an unwanted portion of the input signal (which arrives DIRECTLY via R2 at the output node) causes an unwanted output voltage across r-out. That is the primary reason for the observed behaviour.


Correction:  My answer above is - in principle - correct and the described effect does exist. However, the result of the mentioned &quot;direct coupling effect&quot; is not the primary cause of the observed behaviour. I have performed a simulation by myself under open-loop conditions - and the result is as follows:
The gain and phase enhancement in the region at app. 1 MHz is caused by a kind of internal frequency compensation which ensures stability even in case of unity feedback (most critical situation). Perhaps this frequency compensation in the used opamp model (from LT) is somewhat &quot;stronger&quot; than in the real device (more gain-phase enhancement).
However, such open-loop gain responses as shown in data books should be always regarded as &quot;typical&quot; only. For example, the shown maximum gain of nearly 150 dB will certainly has an uncertainty (tolerance) of 10 dB or so....