In theory yes. In practice, not always as easily.
1Gbit/s is essentially the bit-rate standard on the wire. The ethernet ports may be connected to a back-end bus that has limited bandwidth, especially if you're combining multiple.
Example: there are many dual USB3.0 to PCI-e 1x computer addon cards. USB3.0 can go up to 5Gbit throughput, but PCI-e 2.0 1x (common at the time of USB3.0 going mainstream) only goes up to 4Gbit/s data bandwidth. So although it adds 2x USB3.0 ports, it can not even (or barely as @alex.forenich pointed out) saturate a single port.
Additionally ethernet uses rather small packets to transfer data. At 1500 bytes max. payload, you can have up to 81000 packets/second at 1Gbit/s traffic. If each packet is handled individually via interrupts, that can build up to a lot of CPU time. This could be improved by using jumbo frames.
The protocol used may not scale with multiple connections. E.g. some (high-end) switches may support link aggregation, but only can provide the double bandwidth over multiple TCP connections.