Excel can be infuriating when it comes to charts. If you have Years in Column A and Values in Column B, selected them and inserted a line chart you probably ended up with both columns plotted against 'point number'. Not very helpful :o(
Try this. Select Columns A and B and insert a Scatter chart. You can then either right click a point on the chart and select Format data series and add lines and suppress the points OR if you right click the chart and select Change Chart Type you should be able to get a line chart.
How are you valuing the highs and lows - salary?